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Article Contents

1. introduction, 2. studies of migration studies, 3. methodology, 4. metadata on migration studies, 5. topic clusters in migration studies, 6. trends in topic networks in migration studies, 7. conclusions, acknowledgements.

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Mapping migration studies: An empirical analysis of the coming of age of a research field

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Asya Pisarevskaya, Nathan Levy, Peter Scholten, Joost Jansen, Mapping migration studies: An empirical analysis of the coming of age of a research field, Migration Studies , Volume 8, Issue 3, September 2020, Pages 455–481, https://doi.org/10.1093/migration/mnz031

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Migration studies have developed rapidly as a research field over the past decades. This article provides an empirical analysis not only on the development in volume and the internationalization of the field, but also on the development in terms of topical focus within migration studies over the past three decades. To capture volume, internationalisation, and topic focus, our analysis involves a computer-based topic modelling of the landscape of migration studies. Rather than a linear growth path towards an increasingly diversified and fragmented field, as suggested in the literature, this reveals a more complex path of coming of age of migration studies. Although there seems to be even an accelerated growth for migration studies in terms of volume, its internationalisation proceeds only slowly. Furthermore, our analysis shows that rather than a growth of diversification of topics within migration topic, we see a shift between various topics within the field. Finally, our study shows that there is no consistent trend to more fragmentation in the field; in contrast, it reveals a recent recovery of connectedness between the topics in the field, suggesting an institutionalisation or even theoretical and conceptual coming of age of migration studies.

Migration studies have developed rapidly as a research field in recent decades. It encompasses studies on all types of international and internal migration, migrants, and migration-related diversity ( King, 2002 ; Scholten, 2018 ). Many scholars have observed the increase in the volume of research on migration ( Massey et al., 1998 ; Bommes and Morawska, 2005 ; Scholten et al., 2015 ). Additionally, the field has become increasingly varied in terms of links to broader disciplines ( King, 2012 ; Brettell and Hollifield, 2014 ) and in terms of different methods used ( Vargas-Silva, 2012 ; Zapata-Barrero and Yalaz, 2018 ). It is now a field that has in many senses ‘come of age’: it has internationalised with scholars involved from many countries; it has institutionalised through a growing number of journals; an increasing number of institutes dedicated to migration studies; and more and more students are pursuing migration-related courses. These trends are also visible in the growing presence of international research networks in the field of migration.

Besides looking at the development of migration in studies in terms of size, interdisciplinarity, internationalisation, and institutionalisation, we focus in this article on the development in topical focus of migration studies. We address the question how has the field of migration studies developed in terms of its topical focuses? What topics have been discussed within migration studies? How has the topical composition of the field changed, both in terms of diversity (versus unity) and connectedness (versus fragmentation)? Here, the focus is not on influential publications, authors, or institutes, but rather on what topics scholars have written about in migration studies. The degree of diversity among and connectedness between these topics, especially in the context of quantitative growth, will provide an empirical indication of whether a ‘field’ of migration studies exists, or to what extent it is fragmented.

Consideration of the development of migration studies invokes several theoretical questions. Various scholars have argued that the growth of migration studies has kept pace not only with the growing prominence of migration itself but also with the growing attention of nation–states in particular towards controlling migration. The coproduction of knowledge between research and policy, some argue ( Scholten, 2011 ), has given migration research an inclination towards paradigmatic closure, especially around specific national perspectives on migration. Wimmer and Glick Schiller (2002 ) speak in this regard of ‘methodological nationalism’, and others refer to the prominence of national models that would be reproduced by scholars and policymakers ( Bommes and Morawska, 2005 ; Favell, 2003 ). More generally, this has led, some might argue, to an overconcentration of the field on a narrow number of topics, such as integration and migration control, and a consequent call to ‘de-migranticise’ migration research ( Dahinden, 2016 ; see also Schinkel, 2018 ).

However, recent studies suggest that the growth of migration studies involves a ‘coming of age’ in terms of growing diversity of research within the field. This diversification of migration studies has occurred along the lines of internationalisation ( Scholten et al., 2015 ), disciplinary variation ( Yans-McLaughlin, 1990 ; King, 2012 ; Brettell and Hollifield, 2014 ) and methodological variation ( Vargas-Silva, 2012 ; Zapata-Barrero and Yalaz, 2018 ). The International Organization for Migration ( IOM, 2017 : 95) even concludes that ‘the volume, diversity, and growth of both white and grey literature preclude a [manual] systematic review’ of migration research produced in 2015 and 2016 alone .

Nonetheless, in this article, we attempt to empirically trace the development of migration studies over the past three decades, and seek to find evidence for the claim that the ‘coming of age’ of migration studies indeed involves a broadening of the variety of topics within the field. We pursue an inductive approach to mapping the academic landscape of >30 years of migration studies. This includes a content analysis based on a topic modelling algorithm, applied to publications from migration journals and book series. We trace the changes over time of how the topics are distributed within the corpus and the extent to which they refer to one another. We conclude by giving a first interpretation of the patterns we found in the coming of age of migration studies, which is to set an agenda for further studies of and reflection on the development of this research field. While migration research is certainly not limited to journals and book series that focus specifically on migration, our methods enable us to gain a representative snapshot of what the field looks like, using content from sources that migration researchers regard as relevant.

Migration has always been studied from a variety of disciplines ( Cohen, 1996 ; Brettell and Hollifield, 2014 ), such as economics, sociology, history, and demography ( van Dalen, 2018 ), using a variety of methods ( Vargas-Silva, 2012 ; Zapata-Barrero and Yalaz, 2018 ), and in a number of countries ( Carling, 2015 ), though dominated by Northern Hemisphere scholarship (see, e.g. Piguet et al., 2018 ), especially from North America and Europe ( Bommes and Morawska, 2005 ). Taking stock of various studies on the development of migration studies, we can define several expectations that we will put to an empirical test.

Ravenstein’s (1885) 11 Laws of Migration is widely regarded as the beginning of scholarly thinking on this topic (see Zolberg, 1989 ; Greenwood and Hunt, 2003 ; Castles and Miller, 2014 ; Nestorowicz and Anacka, 2018 ). Thomas and Znaniecki’s (1918) five-volume study of Polish migrants in Europe and America laid is also noted as an early example of migration research. However, according to Greenwood and Hunt (2003 ), migration research ‘took off’ in the 1930s when Thomas (1938) indexed 191 studies of migration across the USA, UK, and Germany. Most ‘early’ migration research was quantitative (see, e.g. Thornthwaite, 1934 ; Thomas, 1938 ). In addition, from the beginning, migration research developed with two empirical traditions: research on internal migration and research on international migration ( King and Skeldon, 2010 ; Nestorowicz and Anacka, 2018 : 2).

In subsequent decades, studies of migration studies describe a burgeoning field. Pedraza-Bailey (1990) refers to a ‘veritable boom’ of knowledge production by the 1980s. A prominent part of these debates focussed around the concept of assimilation ( Gordon, 1964 ) in the 1950s and 1960s (see also Morawska, 1990 ). By the 1970s, in light of the civil rights movements, researchers were increasingly focussed on race and ethnic relations. However, migration research in this period lacked an interdisciplinary ‘synthesis’ and was likely not well-connected ( Kritz et al., 1981 : 10; Pryor, 1981 ; King, 2012 : 9–11). Through the 1980s, European migration scholarship was ‘catching up’ ( Bommes and Morawska, 2005 : 14) with the larger field across the Atlantic. Substantively, research became increasingly mindful of migrant experiences and critical of (national) borders and policies ( Pedraza-Bailey, 1990 : 49). King (2012) also observes this ‘cultural turn’ towards more qualitative anthropological migration research by the beginning of the 1990s, reflective of trends in social sciences more widely ( King, 2012 : 24). In the 1990s, Massey et al. (1993, 1998 ) and Massey (1994) reflected on the state of the academic landscape. Their literature review (1998) notes over 300 articles on immigration in the USA, and over 150 European publications. Despite growth, they note that the field did not develop as coherently in Europe at it had done in North America (1998: 122).

We therefore expect to see a significant growth of the field during the 1980s and 1990s, and more fragmentation, with a prominence of topics related to culture and borders.

At the turn of the millennium, Portes (1997) lists what were, in his view, the five key themes in (international) migration research: 1 transnational communities; 2 the new second generation; 3 households and gender; 4 states and state systems; and 5 cross-national comparisons. This came a year after Cohen’s review of Theories of Migration (1996), which classifies nine key thematic ‘dyads’ in migration studies, such as internal versus international migration; individual versus contextual reasons to migrate; temporary versus permanent migration; and push versus pull factors (see full list in Cohen, 1996 : 12–15). However, despite increasing knowledge production, Portes argues that the problem in these years was the opposite of what Kritz et al. (1981) observe above; scholars had access to and generated increasing amounts of data, but failed to achieve ‘conceptual breakthrough’ ( Portes, 1997 : 801), again suggesting fragmentation in the field.

Thus, in late 1990s and early 2000s scholarship we expect to find a prominence of topics related to these five themes, and a limited number of “new” topics.

In the 21st century, studies of migration studies indicate that there has been a re-orientation away from ‘states and state systems’. This is exemplified by Wimmer and Glick Schiller’s (2002) widely cited commentary on ‘methodological nationalism’, and the alleged naturalisation of nation-state societies in migration research (see Thranhardt and Bommes, 2010 ), leading to an apparent pre-occupation with the integration paradigm since the 1980s according to Favell (2003) and others ( Dahinden, 2016 ; Schinkel, 2018 ). This debate is picked up in Bommes and Morawska’s (2005) edited volume, and Lavenex (2005) . Describing this shift, Geddes (2005) , in the same volume, observes a trend of ‘Europeanised’ knowledge production, stimulated by the research framework programmes of the EU. Meanwhile, on this topic, others highlight a ‘local turn’ in migration and diversity research ( Caponio and Borkert, 2010 ; Zapata-Barrero et al., 2017) .

In this light, we expect to observe a growth in references to European (and other supra-national) level and local-level topics in the 21t century compared to before 2000.

As well as the ‘cultural turn’ mentioned above, King (2012 : 24–25) observes a re-inscription of migration within wider social phenomena—in terms of changes to the constitutive elements of host (and sending) societies—as a key development in recent migration scholarship. Furthermore, transnationalism, in his view, continues to dominate scholarship, though this dominance is disproportionate, he argues, to empirical reality. According to Scholten (2018) , migration research has indeed become more complex as the century has progressed. While the field has continued to grow and institutionalise thanks to networks like International Migration, Integration and Social Cohesion in Europe (IMISCOE) and Network of Migration Research on Africa (NOMRA), this has been in a context of apparently increasing ‘fragmentation’ observed by several scholars for many years (see Massey et al., 1998 : 17; Penninx et al., 2008 : 8; Martiniello, 2013 ; Scholten et al., 2015 : 331–335).

On this basis, we expect a complex picture to emerge for recent scholarship, with thematic references to multiple social phenomena, and a high level of diversity within the topic composition of the field. We furthermore expect increased fragmentation within migration studies in recent years.

The key expectation of this article is, therefore, that the recent topical composition of migration studies displays greater diversity than in previous decades as the field has grown. Following that logic, we hypothesise that with diversification (increasingly varied topical focuses), fragmentation (decreasing connections between topics) has also occurred.

The empirical analysis of the development in volume and topic composition of migration studies is based on the quantitative methods of bibliometrics and topic modelling. Although bibliometric analysis has not been widely used in the field of migration (for some exceptions, see Carling, 2015 ; Nestorowicz and Anacka, 2018 ; Piguet et al., 2018 ; Sweileh et al., 2018 ; van Dalen, 2018 ), this type of research is increasingly popular ( Fortunato et al., 2018 ). A bibliometric analysis can help map what Kajikawa et al. (2007) call an ‘academic landscape’. Our analysis pursues a similar objective for the field of migration studies. However, rather than using citations and authors to guide our analysis, we extract a model of latent topics from the contents of abstracts . In other words, we are focussed on the landscape of content rather than influence.

3.1 Topic modelling

Topic modelling involves a computer-based strategy for identifying topics or topic clusters that figure centrally in a specific textual landscape (e.g. Jiang et al., 2016 ). This is a class of unsupervised machine learning techniques ( Evans and Aceves, 2016 : 22), which are used to inductively explore and discover patterns and regularities within a corpus of texts. Among the most widely used topic models is Latent Dirichlet Allocation (LDA). LDA is a type of Bayesian probabilistic model that builds on the assumption that each document in a corpus discusses multiple topics in differing proportions. Therefore, Document A might primarily be about Topic 1 (60 per cent), but it also refers to terms associated with Topic 2 (30 per cent), and, to a lesser extent, Topic 3 (10 per cent). A topic, then, is defined as a probability distribution over a fixed vocabulary, that is, the totality of words present in the corpus. The advantage of the unsupervised LDA approach that we take is that it does not limit the topic model to our preconceptions of which topics are studied by migration researchers and therefore should be found in the literature. Instead, it allows for an inductive sketching of the field, and consequently an element of surprise ( Halford and Savage, 2017 : 1141–1142). To determine the optimal number of topics, we used the package ldatuning to calculate the statistically optimal number of topics, a number which we then qualitatively validated.

The chosen LDA model produced two main outcomes. First, it yielded a matrix with per-document topic proportions, which allow us to generate an idea of the topics discussed in the abstracts. Secondly, the model returned a matrix with per-topic word probabilities. Essentially, the topics are a collection of words ordered by their probability of (co-)occurrence. Each topic contains all the words from all the abstracts, but some words have a much higher likelihood to belong to the identified topic. The 20–30 most probable words for each topic can be helpful in understanding the content of the topic. The third step we undertook was to look at those most probable words by a group of experts familiar with the field and label them. We did this systematically and individually by first looking at the top 5 words, then the top 30, trying to find an umbrella label that would summarize the topic. The initial labels suggested by each of us were then compared and negotiated in a group discussion. To verify the labels even more, in case of a doubt, we read several selected abstracts marked by the algorithm as exhibiting a topic, and through this were able to further refine the names of the topics.

It is important to remember that this list of topics should not be considered a theoretically driven attempt to categorize the field. It is purely inductive because the algorithm is unable to understand theories, conceptual frames, and approaches; it makes a judgement only on the basis of words. So if words are often mentioned together, the computer regards their probability of belonging to one topic as high.

3.2 Dataset of publications

For the topic modelling, we created a dataset that is representative of publications relevant to migration studies. First, we identified the most relevant sources of literature. Here we chose not only to follow rankings in citation indices, but also to ask migration scholars, in an expert survey, to identify what they considered to be relevant sources. This survey was distributed among a group of senior scholars associated with the IMISCOE Network; 25 scholars anonymously completed the survey. A set of journals and book series was identified from existing indices (such as Google Scholar, Web of Science, and Scopus) which were then validated and added to by respondents. Included in our eventual dataset were all journals and book series that were mentioned at least by two experts in the survey. The dataset includes 40 journals and 4 book series (see Supplementary Data A). Non-English journals were omitted from data collection because the algorithm can only analyse one language. Despite their influence on the field, we also did not consider broader disciplinary journals (for instance, sociological journals or economic journals) for the dataset. Such journals, we acknowledge, have published some of the most important research in the history of migration studies, but even with their omission, it is still possible to achieve our goal of obtaining a representative snapshot of what migration researchers have studied, rather than who or which papers have been most influential. In addition, both because of the language restriction of the algorithm and because of the Global North’s dominance in the field that is mentioned above ( Bommes and Morawska, 2005 ; Piguet et al., 2018 ), there is likely to be an under-representation of scholarship from the Global South in our dataset.

Secondly, we gathered metadata on publications from the selected journals and book series using the Scopus and Web of Science electronic catalogues, and manually collecting from those sources available on neither Scopus nor Web of Science. The metadata included authors, years, titles, and abstracts. We collected all available data up to the end of 2017. In total, 94 per cent of our metadata originated from Scopus, ∼1 per cent from Web of Science, and 5 per cent was gathered manually. One limitation of our dataset lies in the fact that the electronic catalogue of Scopus, unfortunately, does not list all articles and abstracts ever published by all the journals (their policy is to collect articles and abstracts ‘where available’ ( Elsevier, 2017 )). There was no technical possibility of assessing Scopus or WoS’ proportional coverage of all articles actually published. The only way to improve the dataset in this regard would be to manually collect and count abstracts from journal websites. This is also why many relevant books were not included in our dataset; they are not indexed in such repositories.

In the earliest years of available data, only a few journals were publishing (with limited coverage of this on Scopus) specifically on migration. However, Fig. 1 below demonstrates that the numbers constantly grew between 1959 and 2018. As Fig. 1 shows, in the first 30 years (1959–88), the number of migration journals increased by 15, while in the following three decades (1989–2018), this growth intensified as the number of journals tripled to 45 in the survey (see Supplementary Data A for abbreviations).

Number of journals focussed on migration and migration-related diversity (1959–2018) Source: Own calculations.

Within all 40 journals in the dataset, we were able to access and extract for our analysis 29,844 articles, of which 22,140 contained abstracts. Furthermore, we collected 901 available abstracts of chapters in the 4 book series: 2 series were downloaded from the Scopus index (Immigration and Asylum Law in Europe; Handbook of the Economics of International Migration), and the abstracts of the other 2 series, selected from our expert survey (the IMISCOE Research Series Migration Diasporas and Citizenship), were collected manually. Given the necessity of manually collecting the metadata for 896 abstracts of the chapters in these series, it was both practical and logical to set these two series as the cut-off point. Ultimately, we get a better picture of the academic landscape as a whole with some expert-approved book series than with none .

Despite the limitations of access, we can still have an approximate idea on how the volume of publications changed overtime. The chart ( Fig. 2 ) below shows that both the number of published articles and the number of abstracts of these articles follow the same trend—a rapid growth after the turn of the century. In 2017, there were three times more articles published per year than in 2000.

Publications and abstracts in the dataset (1959–2018).

The cumulative graph ( Fig. 3 ) below shows the total numbers of publications and the available abstracts. For the creation of our inductively driven topic model, we used all available abstracts in the entire timeframe. However, to evaluate the dynamics of topics over time, we decided to limit the timeframe of our chronological analyses to 1986–2017, because as of 1986, there were more than 10 active journals and more articles had abstracts. This analysis therefore covers the topical evolution of migration studies in the past three decades.

Cumulative total of publications and abstracts (1959–2017).

Migration studies has only internationalised very slowly in support of what others have previously argued ( Bommes and Morawska, 2005 ; Piguet et al., 2018 ). Figure 4 gives a snapshot of the geographic dispersion of the articles (including those without abstracts) that we collected from Scopus. Where available, we extracted the country of authors’ university affiliations. The colour shades represent the per capita publication volume. English-language migration scholarship has been dominated by researchers based, unsurprisingly, in Anglophone and Northern European countries.

Migration research output per capita (based on available affiliation data within dataset).

The topic modelling (following the LDA model) led us, as discussed in methods, to the definition of 60 as the optimal number of topics for mapping migration studies. Each topic is a string of words that, according to the LDA algorithm, belong together. We reviewed the top 30 words for each word string and assigned labels that encapsulated their meaning. Two of the 60 word strings were too generic and did not describe anything related to migration studies; therefore, we excluded them. Subsequently, the remaining 58 topics were organised into a number of clusters. In the Table 1 below, you can see all the topic labels, the topic clusters they are grouped into and the first 5 (out of 30) most probable words defining those topics.

Topics in migration studies

After presenting all the observed topics in the corpus of our publication data, we examined which topics and topic clusters are most frequent in general (between 1964 and 2017), and how their prominence has been changing over the years. On the basis of the matrix of per-item topic proportions generated by LDA analysis, we calculated the shares of each topic in the whole corpus. On the level of individual topics, around 25 per cent of all abstract texts is about the top 10 most prominent topics, which you can see in Fig. 5 below. Among those, #56 identity narratives (migration-related diversity), #39 migration theory, and #29 migration flows are the three most frequently detected topics.

Top 10 topics in the whole corpus of abstracts.

On the level of topic clusters, Fig. 6 (left) shows that migration-related diversity (26 per cent) and migration processes (19 per cent) clearly comprise the two largest clusters in terms of volume, also because they have the largest number topics belonging to them. However, due to our methodology of labelling these topics and grouping them into clusters, it is complicated to make comparisons between topic clusters in terms of relative size, because some clusters simply contain more topics. Calculating average proportions of topics within each cluster allows us to control for the number of topics per cluster, and with this measure, we can better compare the relative prominence of clusters. Figure 6 (right) shows that migration research and statistics have the highest average of topic proportions, followed by the cluster of migration processes and immigrant incorporation.

Topic proportions per cluster.

An analysis on the level of topic clusters in the project’s time frame (1986–2017) reveals several significant trends. First, when discussing shifts in topics over time, we can see that different topics have received more focus in different time frames. Figure 7 shows the ‘age’ of topics, calculated as average years weighted by proportions of publications within a topic per year. The average year of the articles on the same topic is a proxy for the age of the topic. This gives us an understanding of which topics were studied more often compared with others in the past and which topics are emerging. Thus, an average year can be understood as the ‘high-point’ of a topic’s relative prominence in the field. For instance, the oldest topics in our dataset are #22 ‘Migrant demographics’, followed by #45 ‘Governance of migration’ and #46 ‘Migration statistics and survey research’. The newest topics include #14 ‘Mobilities’ and #48 ‘Intra-EU mobility’.

Average topic age, weighted by proportions of publications (publications of 1986–2017). Note: Numbers near dots indicate the numeric id of topics (see Table 1 for the names).

When looking at the weighted ‘age’ of the clusters, it becomes clear that the focus on migration research and statistics is the ‘oldest’, which echoes what Greenwood and Hunt (2003 ) observe. This resonates with the idea that migration studies has roots in more demographic studies of migration and diversity (cf. Thornthwaite, 1934 ; Thomas, 1938 ), which somewhat contrasts with what van Dalen (2018) has found. Geographies of migration (studies related to specific migration flows, origins, and destinations) were also more prominent in the 1990s than now, and immigrant incorporation peaked at the turn of the century. However, gender and family, diversity, and health are more recent themes, as was mentioned above (see Fig. 8 ). This somewhat indicates a possible post-methodological nationalism, post-integration paradigm era in migration research going hand-in-hand with research that, as King (2012) argues, situates migration within wider social and political domains (cf. Scholten, 2018 ).

Diversity of topics and topic clusters (1985–2017).

Then, we analysed the diversification of publications over the various clusters. Based on the literature review, we expected the diversification to have increased over the years, signalling a move beyond paradigmatic closure. Figure 9 (below) shows that we can hardly speak of a significant increase of diversity in migration studies publications. Over the years, only a marginal increase in the diversity of topics is observed. The Gini-Simpson index of diversity in 1985 was around 0.95 and increased to 0.98 from 1997 onwards. Similarly, there is little difference between the sizes of topic clusters over the years. Both ways of calculating the Gini-Simpson index of diversity by clusters resulted in a rather stable picture showing some fluctuations between 0.82 and 0.86. This indicates that there has never been a clear hegemony of any cluster at any time. In other words, over the past three decades, the diversity of topics and topic clusters was quite stable: there have always been a great variety of topics discussed in the literature of migration studies, with no topic or cluster holding a clear monopoly.

Average age of topic clusters, weighted by proportions (publications of 1986–2017).

Subsequently, we focussed on trends in topic networks. As our goal is to describe the general development of migration studies as a field, we decided to analyse topic networks in three equal periods of 10 years (Period 1 (1988–97); Period 2 (1998–2007); Period 3 (2008–17)). On the basis of the LDA-generated matrix with per-abstract topic proportions (The LDA algorithm determines the proportions of all topics observed within each abstract. Therefore, each abstract can contain several topics with a substantial prominence), we calculated the topic-by-topic Spearman correlation coefficients in each of the time frames. From the received distribution of the correlation coefficients, we chose to focus on the top 25 per cent strongest correlations period. In order to highlight difference in strength of connections, we assigned different weights to the correlations between the topics. Coefficient values above the 75th percentile (0.438) but ≤0.5 were weighted 1; correlations above 0.5 but ≤0.6 were weighted 2; and correlations >0.6 were weighted 3. We visualised these topic networks using the software Gephi.

To compare networks of topics in each period, we used three common statistics of network analysis: 1 average degree of connections; 2 average weighted degree of connections; and 3 network density. The average degree of connections shows how many connections to other topics each topic in the network has on average. This measure can vary from 0 to N − 1, where N is the total number of topics in the network. Some correlations of topics are stronger and were assigned the Weight 2 or 3. These are included in the statistics of average weighted degree of connections, which shows us the variations in strength of existing connections between the topics. Network density is a proportion of existing links over the number of all potentially possible links between the topics. This measure varies from 0 = entirely disconnected topics to 1 = extremely dense network, where every topic is connected to every topic.

Table 2 shows that all network measures vary across the three periods. In Period 1, each topic had on average 21 links with other topics, while in Period 2, that number was much lower (11.5 links). In Period 3, the average degree of connections grew again, but not to the level of Period 1. The same trend is observed in the strength of these links—in Period 1, the correlations between the topics were stronger than in Period 3, while they were the weakest in Period 2. The density of the topic networks was highest in Period 1 (0.4), then in Period 2, the topic network became sparser before densifying again in Period 3 (but not to the extent of Period 1’s density).

Topic network statistics

These fluctuations on network statistics indicate that in the years 1988–97, topics within the analysed field of migration studies were mentioned in the same articles and book chapters more often, while at the turn of the 21st century, these topic co-occurrences became less frequent; publications therefore became more specialised and topics were more isolated from each other. In the past 10 years, migration studies once again became more connected, the dialogues between the topics emerged more frequently. These are important observations about topical development in the field of migration studies. The reasons behind these changes require further, possibly more qualitative explanation.

To get a more in-depth view of the content of these topic networks, we made an overview of the changes in the topic clusters across the three periods. As we can see in Fig. 10 , some changes emerge in terms of the prominence of various clusters. The two largest clusters (also by the number of topics within them) are migration-related diversity and migration processes. The cluster of migration-related diversity increased in its share of each period’s publications by around 20 per cent. This reflects our above remarks on the literature surrounding the integration debate, and the ‘cultural turn’ King mentions (2012). And the topic cluster migration processes also increased moderately its share.

Prominence and change in topic clusters 1988–2017.

Compared with the first period, the topic cluster of gender and family studies grew the fastest, with the largest growth observed in the turn of the century (relative to its original size). This suggests a growing awareness of gender and family-related aspects of migration although as a percentage of the total corpus it remains one the smallest clusters. Therefore, Massey et al.’s (1998) argument that households and gender represented a quantitatively significant pillar of migration research could be considered an overestimation. The cluster of health studies in migration research also grew significantly in the Period 2 although in Period 3, the percentage of publications in this cluster diminished. This suggests a rising awareness of health in relation to migration and diversity (see Sweileh et al., 2018 ) although this too remains one of the smallest clusters.

The cluster on Immigrant incorporation lost prominence the most over the past 30 years. This seems to resonate with the argument that ‘integrationism’ or the ‘integration paradigm’ was rather in the late 1990s (see Favell, 2003 ; Dahinden, 2016 ) and is losing its prominence. A somewhat slower but steady loss was also observed in the cluster of Geographies of migration and Migration research and statistics. This also suggests not only a decreasing emphasis on demographics within migration studies, but also a decreasing reflexivity in the development of the field and the focus on theory-building.

We will now go into more detail and show the most connected topics and top 10 most prominent topics in each period. Figures 11–13 show the network maps of topics in each period. The size of circles reflects the number and strength of links per each topic: the bigger the size, the more connected this topic is to the others; the biggest circles indicate the most connected topics. While the prominence of a topic is measured by the number of publications on that topic, it is important to note that the connectedness the topic has nothing necessarily to do with the amount of publications on that topic; in theory, a topic could appear in many articles without any reference to other topics (which would mean that it is prominent but isolated).

Topic network in 1988–97. Note: Numbers indicate topics' numerical ids, see Table 1 for topics' names.

Topic network in 1998–2007. Note: Numbers indicate topics' numerical ids, see Table 1 for topics' names.

Topic network in 2008–2017. Note: Numbers indicate topics' numerical ids, see Table 1 for topics' names.

Thus, in the section below, we describe the most connected and most prominent topics in migration research per period. The degree of connectedness is a useful indicator of the extent to which we can speak of a ‘field’ of migration research. If topics are well-connected, especially in a context of increased knowledge production and changes in prominence among topics, then this would suggest that a shared conceptual and theoretical language exists.

6.1 Period 1: 1988–97

The five central topics with the highest degree of connectedness (the weighted degree of connectedness of these topics was above 60) were ‘black studies’, ‘mobilities’, ‘ICT, media and migration’, ‘migration in/from Israel and Palestine’, and ‘intra-EU mobility’. These topics are related to geopolitical regions, ethnicity, and race. The high degree of connectedness of these topics shows that ‘they often occurred together with other topics in the analysed abstracts from this period’. This is expected because research on migration and diversity inevitably discusses its subject within a certain geographical, political, or ethnic scope. Geographies usually appear in abstracts as countries of migrants’ origin or destination. The prominence of ‘black studies’ reflects the dominance of American research on diversity, which was most pronounced in this period ( Fig. 11 ).

The high degree of connectedness of the topics on ICT and ‘media’ is indicative of wider societal trends in the 1990s. As with any new phenomenon, it clearly attracted the attention of researchers who wanted to understand its relationship with migration issues.

Among the top 10 topics with the most publications in this period (see Supplementary Data B) were those describing the characteristics of migration flows (first) and migration populations (third). It goes in line with the trends of the most connected topics described above. Interest in questions of migrants’ socio-economic position (fourth) in the receiving societies and discussion on ‘labour migration’ (ninth) were also prevalent. Jointly, these topics confirm that in the earlier years, migration was ‘studied often from the perspectives of economics and demographics’ ( van Dalen, 2018 ).

Topics, such as ‘education and language training’ (second), community development’ (sixth), and ‘intercultural communication’ (eighth), point at scholarly interest in the issues of social cohesion and socio-cultural integration of migrants. This lends strong support to Favell’s ‘integration paradigm’ argument about this period and suggests that the coproduction of knowledge between research and policy was indeed very strong ( Scholten, 2011 ). This is further supported by the prominence of the topic ‘governance of migration’ (seventh), reflecting the evolution of migration and integration policymaking in the late 1980s and beginning of the 1990s, exemplified by the development of the Schengen area and the EU more widely; governance of refugee flows from the Balkan region (also somewhat represented in the topic ‘southern-European migration’, which was the 10th most prominent); and governance of post-Soviet migration. Interestingly, this is the only period in which ‘migration histories’ is among the top 10 topics, despite the later establishment of a journal dedicated to the very discipline of history. Together these topics account for 42 per cent of all migration studies publications in that period of time.

6.2 Period 2: 1998–2007

In the second period, as the general degree of connectedness in the topic networks decreased, the following five topics maintained a large number of connections in comparison to others, as their average weighted degree of connections ranged between 36 and 57 ties. The five topics were ‘migration in/from Israel and Palestine’, ‘black studies’, ‘Asian migration’, ‘religious diversity’, and ‘migration, sexuality, and health’ ( Fig. 12 ).

Here we can observe the same geographical focus of the most connected topics, as well as the new trends in the migration research. ‘Asian migration’ became one of the most connected topics, meaning that migration from/to and within that region provoked more interest of migration scholars than in the previous decade. This development appears to be in relation to high-skill migration, in one sense, because of its strong connections with the topics ‘Asian expat migration’ and ‘ICT, media, and migration’; and, in another sense, in relation to the growing Muslim population in Europe thanks to its strong connection to ‘religious diversity’. The high connectedness of the topic ‘migration sexuality and health’ can be explained by the dramatic rise of the volume of publications within the clusters ‘gender and family’ studies and ‘health’ in this time-frame as shown in the charts on page 13, and already argued by Portes (1997) .

In this period, ‘identity narratives’ became the most prominent topic (see Supplementary Data B), which suggests increased scholarly attention on the subjective experiences of migrants. Meanwhile ‘migrant flows’ and ‘migrant demographics’ decreased in prominence from the top 3 to the sixth and eighth position, respectively. The issues of education and socio-economic position remained prominent. The emergence of topics ‘migration and diversity in (higher) education’ (fifth) and ‘cultural diversity’ (seventh) in the top 10 of this period seem to reflect a shift from integrationism to studies of diversity. The simultaneous rise of ‘migration theory’ (to fourth) possibly illustrates the debates on methodological nationalism which emerged in the early 2000s. The combination of theoretical maturity and the intensified growth in the number of migration journals at the turn of the century suggests that the field was becoming institutionalised.

Overall, the changes in the top 10 most prominent topics seem to show a shifting attention from ‘who’ and ‘what’ questions to ‘how’ and ‘why’ questions. Moreover, the top 10 topics now account only for 26 per cent of all migration studies (a 15 per cent decrease compared with the period before). This means that there were many more topics which were nearly as prominent as those in the top 10. Such change again supports our claim that in this period, there were more intensive ‘sub-field’ developments in migration studies than in the previous period.

6.3 Period 3: 2008–17

In the last decade, the most connected topics have continued to be: ‘migration in/from Israel and Palestine’, ‘Asian migration’, and ‘black studies’. The hypothetical reasons for their central position in the network of topics are the same as in the previous period. The new most-connected topics—‘Conflicts, violence, and migration’, together with the topic ‘Religious diversity’—might indicate to a certain extent the widespread interest in the ‘refugee crisis’ of recent years ( Fig. 13 ).

The publications on the top 10 most prominent topics constituted a third of all migration literature of this period analysed in our study. A closer look at them reveals the following trends (see Supplementary Data B for details). ‘Mobilities’ is the topic of the highest prominence in this period. Together with ‘diasporas and transnationalism’ (fourth), this reflects the rise of critical thinking on methodological nationalism ( Wimmer and Glick Schiller, 2002 ) and the continued prominence of transnationalism in the post-‘mobility turn’ era ( Urry (2007) , cited in King, 2012 ).

The interest in subjective experiences of migration and diversity has continued, as ‘identity narratives’ continues to be prominent, with the second highest proportion of publications, and as ‘Discrimination and socio-psychological issues’ have become the eighth most prominent topic. This also echoes an increasing interest in the intersection of (mental) health and migration (cf. Sweileh et al., 2018 ).

The prominence of the topics ‘human rights law and protection’ (10th) and ‘governance of migration and diversity’ (9th), together with ‘conflicts, violence, and migration’ being one of the most connected topics, could be seen as a reflection of the academic interest in forced migration and asylum. Finally, in this period, the topics ‘race and racism’ (fifth) and ‘black studies’ (seventh) made it into the top 10. Since ‘black studies’ is also one of the most connected topics, such developments may reflect the growing attention to structural and inter-personal racism not only in the USA, perhaps reflecting the #blacklivesmatter movement, as well as in Europe, where the idea of ‘white Europeanness’ has featured in much public discourse.

6.4 Some hypotheses for further research

Why does the connectedness of topics change across three periods? In an attempt to explain these changes, we took a closer look at the geographical distribution of publications in each period. One of the trends that may at least partially explain the loss of connectedness between the topics in Period 2 could be related to the growing internationalisation of English language academic literature linked to a sharp increase in migration-focussed publications during the 1990s.

Internationalisation can be observed in two ways. First, the geographies of English language journal publications have become more diverse over the years. In the period 1988–97, the authors’ institutional affiliations spanned 57 countries. This increased to 72 in 1998–2007, and then to 100 in 2007–18 (we counted only those countries which contained at least 2 publications in our dataset). Alongside this, even though developed Anglophone countries (the USA, Canada, Australia, the UK, Ireland, and New Zealand) account for the majority of publications of our overall dataset, the share of publications originating from non-Anglophone countries has increased over time. In 1988–97, the number of publications from non-Anglophone European (EU+EEA) countries was around 13 per cent. By 2008–17, this had significantly increased to 28 per cent. Additionally, in the rest of the world, we observe a slight proportional increase from 9.5 per cent in the first period to 10.6 per cent in the last decade. Developed Anglophone countries witness a 16 per cent decrease in their share of all articles on migration. The trends of internationalisation illustrated above, combined with the loss of connectedness at the turn of the 21st century, seem to indicate that English became the lingua-franca for academic research on migration in a rather organic manner.

It is possible that a new inflow of ideas came from the increased number of countries publishing on migration whose native language is not English. This rise in ‘competition’ might also have catalysed innovation in the schools that had longer established centres for migration studies. Evidence for this lies in the rise in prominence of the topic ‘migration theory’ during this period. It is also possible that the expansion of the European Union and its research framework programmes, as well as the Erasmus Programmes and Erasmus Mundus, have perhaps brought novel, comparative, perspectives in the field. All this together might have created fruitful soil for developing unique themes and approaches, since such approaches in theory lead to more success and, crucially, more funds for research institutions.

This, however, cannot fully explain why in Period 3 the field became more connected again, other than that the framework programmes—in particular framework programme 8, Horizon 2020—encourage the building of scientific bridges, so to speak. Our hypothesis is thus that after the burst of publications and ideas in Period 2, scholars began trying to connect these new themes and topics to each other through emergent international networks and projects. Perhaps even the creation and work of the IMISCOE (2004-) and NOMRA (1998-) networks contributed to this process of institutionalisation. This, however, requires much further thought and exploration, but for now, we know that the relationship between the growth, the diversification, and the connectedness in this emergent research field is less straightforward than we might previously have suggested. This begs for further investigation perhaps within a sociology of science framework.

This article offers an inductive mapping of the topical focus of migration studies over a period of more than 30 years of development of the research field. Based on the literature, we expected to observe increasing diversity of topics within the field and increasing fragmentation between the topics, also in relation to the rapid growth in volume and internationalisation of publications in migration studies. However, rather than growth and increased diversity leading to increased fragmentation, our analysis reveals a complex picture of a rapidly growing field where the diversity of topics has remained relatively stable. Also, even as the field has internationalised, it has retained its overall connectedness, albeit with a slight and temporary fragmentation at the turn of the century. In this sense, we can argue that migration studies have indeed come of age as a distinct research field.

In terms of the volume of the field of migration studies, our study reveals an exponential growth trajectory, especially since the mid-1990s. This involves both the number of outlets and the number of publications therein. There also seems to be a consistent path to internationalisation of the field, with scholars from an increasing number of countries publishing on migration, and a somewhat shrinking share of publications from Anglo-American countries. However, our analysis shows that this has not provoked an increased diversity of topics in the field. Instead, the data showed that there have been several important shifts in terms of which topics have been most prominent in migration studies. The field has moved from focusing on issues of demographics, statistics, and governance, to an increasing focus on mobilities, migration-related diversity, gender, and health. Also, interest in specific geographies of migration seems to have decreased.

These shifts partially resonated with the expectations derived from the literature. In the 1980s and 1990s, we observed the expected widespread interest in culture, seen in publications dealing primarily with ‘education and language training’, ‘community development’, and ‘intercultural communication’. This continued to be the case at the turn of the century, where ‘identity narratives’ and ‘cultural diversity’ became prominent. The expected focus on borders in the periods ( Pedraza-Bailey, 1990 ) was represented by the high proportion of research on the ‘governance of migration’, ‘migration flows’, and in the highly connected topic ‘intra-EU mobility’. Following Portes (1997) , we expected ‘transnational communities’, ‘states and state systems’, and the ‘new second generation’ to be key themes for the ‘new century’. Transnationalism shifts attention away from geographies of migration and nation–states, and indeed, our study shows that ‘geographies of migration’ gave way to ‘mobilities’, the most prominent topic in the last decade. This trend is supported by the focus on ‘diasporas and transnationalism’ and ‘identity narratives’ since the 2000s, including literature on migrants’ and their descendants’ dual identities. These developments indicate a paradigmatic shift in migration studies, possibly caused by criticism of methodological nationalism. Moreover, our data show that themes of families and gender have been discussed more in the 21st century, which is in line with Portes’ predictions.

The transition from geographies to mobilities and from the governance of migration to the governance of migration-related diversity, race and racism, discrimination, and social–psychological issues indicates a shifting attention in migration studies from questions of ‘who’ and ‘what’ towards ‘how’ and ‘why’. In other words, a more nuanced understanding of the complexity of migration processes and consequences emerges, with greater consideration of both the global and the individual levels of analysis.

However, this complexification has not led to thematic fragmentation in the long run. We did not find a linear trend towards more fragmentation, meaning that migration studies have continued to be a field. After an initial period of high connectedness of research mainly coming from America and the UK, there was a period with significantly fewer connections within migration studies (1998–2007), followed by a recovery of connectedness since then, while internationalisation has continued. What does this tell us?

We may hypothesise that the young age of the field and the tendency towards methodological nationalism may have contributed to more connectedness in the early days of migration studies. The accelerated growth and internationalisation of the field since the late 1990s may have come with an initial phase of slight fragmentation. The increased share of publications from outside the USA may have caused this, as according to Massey et al. (1998) , European migration research was then more conceptually dispersed than across the Atlantic. The recent recovery of connectedness could then be hypothesised as an indicator of the field’s institutionalisation, especially at the European level, and growing conceptual and theoretical development. As ‘wisdom comes with age’, this may be an indication of the ‘coming of age’ of migration studies as a field with a shared conceptual and theoretical foundation.

The authors would like to thank the three anonymous reviewers for their constructive feedback, as well as dr. J.F. Alvarado for his advice in the early stages of work on this article.

This research is associated with the CrossMigration project, funded by the European Union's Horizon 2020 research and innovation programme under the grant agreement Ares(2017) 5627812-770121.

Conflict of interest statement . None declared.

Bommes M. , Morawska E. ( 2005 ) International Migration Research: Constructions, Omissions and the Promises of Interdisciplinarity . Aldershot : Ashgate .

Google Scholar

Google Preview

Brettell C. B. , Hollifield J. F. ( 2014 ) Migration Theory: Talking across Disciplines . London : Routledge .

Caponio T. , Borkert M. ( 2010 ) The Local Dimension of Migration Policymaking . Amsterdam : Amsterdam University Press .

Carling J. ( 2015 ) Who Is Who in Migration Studies: 107 Names Worth Knowing < https://jorgencarling.org/2015/06/01/who-is-who-in-migration-studies-108-names-worth-knowing/#_Toc420761452 > accessed 1 Jun 2015.

Castles S. , Miller M. J. ( 2014 ) The Age of Migration: International Population Movements in the Modern World , 5th edn. Basingstoke : Palgrave Macmillan .

Cohen R. ( 1996 ) Theories of Migration . Cheltenham : Edward Elgar .

Dahinden J. ( 2016 ) ‘A Plea for the “De-migranticization” of Research on Migration and Integration,’ Ethnic and Racial Studies , 39 / 13 : 2207 – 25 .

Elsevier ( 2017 ) Scopus: Content Coverage Guide . < https://www.elsevier.com/__data/assets/pdf_file/0007/69451/0597-Scopus-Content-Coverage-Guide-US-LETTER-v4-HI-singles-no-ticks.pdf > accessed 18 Dec 2018.

Evans J. A. , Aceves P. ( 2016 ) ‘Machine Translation: Mining Text for Social Theory,’ Annual Review of Sociology’ , 42 / 1 : 21 – 50 .

Favell A. ( 2003 ) ‘Integration Nations: The Nation-State and Research on Immigrants in Western Europe’, in Brochmann G. , ed. The Multicultural Challenge , pp. 13 – 42 . Bingley : Emerald .

Fortunato S. , et al.  ( 2018 ) ‘Science of Science’ , Science , 359 / 6379 : 1 – 7 .

Geddes A. ( 2005 ) ‘Migration Research and European Integration: The Construction and Institutionalization of Problems of Europe’, in Bommes M. , Morawska E. (eds). International Migration Research: Constructions, Omissions and the Promises of Interdisciplinarity , pp. 265 – 280 . Aldershot : Ashgate .

Gordon M. ( 1964 ) Assimilation in American Life . New York : Oxford University Press .

Greenwood M. J. , Hunt G. L. ( 2003 ) ‘The Early History of Migration Research,’ International Regional Sciences Review , 26 / 1 : 3 – 37 .

Halford S. , Savage M. ( 2017 ) ‘Speaking Sociologically with Big Data: Symphonic Social Science and the Future for Big Data Research,’ Sociology , 51 / 6 : 1132 – 48 .

IOM ( 2017 ) ‘Migration Research and Analysis: Growth, Reach and Recent Contributions’, in IOM, World Migration Report 2018 , pp. 95 – 121 . Geneva : International Organization for Migration .

Jiang H. , Qiang M. , Lin P. ( 2016 ) ‘A Topic Modeling Based Bibliometric Exploratoin of Hydropower Research,’ Renewable and Sustainable Energy Reviews , 57 : 226 – 37 .

Kajikawa Y. , et al.  ( 2007 ) ‘Creating an Academic Landscape of Sustainability Science: An Analysis of the Citation Network,’ Sustainability Science , 2 / 2 : 221 – 31 .

King R. , Skeldon R. ( 2010 ) ‘Mind the Gap: Integrating Approaches to Internal and International Migration,’ Journal of Ethnic and Migration Studies , 36 / 10 : 1619 – 46 .

King R. , Skeldon R. ( 2002 ) ‘Towards a New Map of European Migration,’ International Journal of Population Geography , 8 / 2 : 89 – 106 .

King R. , Skeldon R. ( 2012 ) Theories and Typologies of Migration: An Overview and a Primer . Malmö : Malmö Institute for Studies of Migration, Diversity and Welfare (MIM ).

Kritz M. M. , Keely C. B. , Tomasi S. M. ( 1981 ) Global Trends in Migration: Theory and Research on International Population Movements . New York : The Centre for Migration Studies .

Lavenex S. ( 2005 ) ‘National Frames in Migration Research: The Tacit Political Agenda’, in Bommes M. , Morawska E. (eds) International Migration Research: Constructions, Omissions and the Promises of Interdisciplinarity , pp. 243 – 263 . Aldershot : Ashgate .

Martiniello M. ( 2013 ) ‘Comparisons in Migration Studies,’ Comparative Migration Studies , 1 / 1 : 7 – 22 .

Massey D. S. , et al.  ( 1993 ) ‘Theories of International Migration: A Review and Appraisal,’ Population and Development Review , 19 / 3 : 431 – 66 .

Massey D. S. ( 1994 ) ‘An Evaluation of International Migration Theory: The North American Case,’ Population and Development Review , 20 / 4 : 699 – 751 .

Massey D. S. , et al.  ( 1998 ) Worlds in Motion: Understanding International Migration at the End of the Millennium . Oxford : Clarendon .

Morawska E. ( 1990 ) ‘The Sociology and Historiography of Immigration’, In Yans-McLaughlin V. , (ed.) Immigration Reconsidered: History, Sociology, and Politics . Oxford : Oxford University Press .

Nestorowicz J. , Anacka M. ( 2018 ) ‘Mind the Gap? Quantifying Interlinkages between Two Traditions in Migration Literature,’ International Migration Review , 53/1 : 1 – 25 .

Pedraza-Bailey S. ( 1990 ) ‘Immigration Research: A Conceptual Map,’ Social Science History , 14 / 1 : 43 – 67 .

Penninx R. , Spencer D. , van Hear N. ( 2008 ) Migration and Integration in Europe: The State of Research . Oxford : ESRC Centre on Migration, Policy and Society .

Piguet E. , Kaenzig R. , Guélat J. ( 2018 ) ‘The Uneven Geography of Research on “Environmental Migration”,’ Population and Environment , 39 / 4 : 357 – 83 .

Portes A. ( 1997 ) ‘Immigration Theory for a New Century: Some Problems and Opportunities,’ International Migration Review , 31 / 4 : 799 – 825 .

Pryor R. J. ( 1981 ) ‘Integrating International and Internal Migration Theories’, in Kritz M. M. , Keely C. B. , Tomasi S. M. (eds) Global Trends in Migration: Theory and Research on International Population Movements , pp. 110 – 129 . New York : The Center for Migration Studies .

Ravenstein G. E. ( 1885 ) ‘The Laws of Migration,’ Journal of the Royal Statistical Society , 48 : 167 – 235 .

Schinkel W. ( 2018 ) ‘Against “Immigrant Integration”: For an End to Neocolonial Knowledge Production,’ Comparative Migration Studies , 6 / 31 : 1 – 17 .

Scholten P. ( 2011 ) Framing Immigrant Integration: Dutch Research-Policy Dialogues in Comparative Perspective . Amsterdam : Amsterdam University Press .

Scholten P. ( 2018 ) Mainstreaming versus Alienation: Conceptualizing the Role of Complexity in Migration and Diversity Policymaking . Rotterdam : Erasmus Universiteit Rotterdam .

Scholten P. , et al.  ( 2015 ) Integrating Immigrants in Europe: Research-Policy Dialogues . Dordrecht : Springer .

Sweileh W. M. , et al.  ( 2018 ) ‘Bibliometric Analysis of Global Migration Health Research in Peer-Reviewed Literature (2000–2016)’ , BMC Public Health , 18 / 777 : 1 – 18 .

Thomas D. S. ( 1938 ) Research Memorandum on Migration Differentials . New York : Social Science Research Council .

Thornthwaite C. W. ( 1934 ) Internal Migration in the United States . Philadelphia, PA : University of Pennsylvania Press .

Thränhardt D. , Bommes M. ( 2010 ) National Paradigms of Migration Research . Göttingen : V&R Unipress .

Urry J. ( 2007 ) Mobilities . Cambridge : Polity .

van Dalen H. ( 2018 ) ‘Is Migration Still Demography’s Stepchild?’ , Demos: Bulletin over Bevolking en Samenleving , 34 / 5 : 8 .

Vargas-Silva C. ( 2012 ) Handbook of Research Methods in Migration . Cheltenham : Edward Elgar .

Wimmer A. , Glick Schiller N. ( 2002 ) ‘Methodological Nationalism and beyond: Nation-State Building, Migration and the Social Sciences,’ Global Networks , 2 / 4 : 301 – 34 .

Yans-McLaughlin V. ( 1990 ) Immigration Reconsidered: History, Sociology, and Politics . Oxford : Oxford University Press .

Zapata-Barrero R. , Yalaz E. ( 2018 ) Qualitative Research in European Migration Studies . Dordrecht : Springer .

Zapata-Barrero R. , Caponio T. , Scholten P. ( 2017 ) ‘Theorizing the “Local Turn” in a Multi-Level Governance Framework of Analysis: A Case Study in Immigrant Policies,’ International Review of Administrative Sciences , 83 / 2 : 241 – 6 .

Zolberg A. R. ( 1989 ) ‘The Next Waves: Migration Theory for a Changing World,’ International Migration Review , 23 / 3 : 403 – 30 .

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McAuliffe, M. and L.A. Oucho (eds.), 2024. World Migration Report 2024. International Organization for Migration (IOM), Geneva.

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World Migration Report 2024

Since 2000, IOM has been producing its flagship world migration reports every two years. The World Migration  Report 2024 , the twelfth in the world migration report series, has been produced to contribute to increased understanding of migration and mobility throughout the world. This new edition presents key data and information on migration as well as thematic chapters on highly topical migration issues, and is structured to focus on two key contributions for readers: Part I: key information on migration and migrants (including migration-related statistics); and Part II: balanced, evidence-based analysis of complex and emerging migration issues.

This flagship World Migration Report has been produced in line with IOM’s Environment Policy and is available online only. Printed hard copies have not been made in order to reduce paper, printing and transportation impacts.

The World Migration Report 2024 interactive page is also available here .

• Editorial, review and production team
• Acknowledgements
• Contributors
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• List of figures and tables
• List of appendices
• Chapter 1 – Report overview: Migration continues to be part of the solution in a rapidly changing world, but key challenges remain
• Chapter 2 – Migration and migrants: A global overview
• Chapter 3 – Migration and migrants: Regional dimensions and developments
• Chapter 4 – Growing migration inequality: What do the global data actually show?
• Chapter 5 – Migration and human security: Unpacking myths and examining new realities and responses
• Chapter 6 – Gender and migration: Trends, gaps and urgent action
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• Chapter 9 – A post-pandemic rebound? Migration and mobility globally after COVID-19

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Migration and health: a global public health research priority

• Kolitha Wickramage 1 ,
• Jo Vearey 2 ,
• Anthony B. Zwi 3 ,
• Courtland Robinson 4 &
• Michael Knipper 5  

BMC Public Health volume  18 , Article number:  987 ( 2018 ) Cite this article

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With 244 million international migrants, and significantly more people moving within their country of birth, there is an urgent need to engage with migration at all levels in order to support progress towards global health and development targets. In response to this, the 2nd Global Consultation on Migration and Health– held in Colombo, Sri Lanka in February 2017 – facilitated discussions concerning the role of research in supporting evidence-informed health responses that engage with migration.

Conclusions

Drawing on discussions with policy makers, research scholars, civil society, and United Nations agencies held in Colombo, we emphasize the urgent need for quality research on international and domestic (in-country) migration and health to support efforts to achieve the Sustainable Development Goals (SDGs). The SDGs aim to ‘leave no-one behind’ irrespective of their legal status. An ethically sound human rights approach to research that involves engagement across multiple disciplines is required. Researchers need to be sensitive when designing and disseminating research findings as data on migration and health may be misused, both at an individual and population level. We emphasize the importance of creating an ‘enabling environment’ for migration and health research at national, regional and global levels, and call for the development of meaningful linkages – such as through research reference groups – to support evidence-informed inter-sectoral policy and priority setting processes.

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Migration and health are increasingly recognized as a global public health priority [ 1 ]. Incorporating mixed flows of economic, forced, and irregular migration, migration has increased in extent and complexity. Globally, it is estimated that there are 244 million international migrants and significantly more internal migrants – people moving within their country of birth [ 2 ]. Whilst the majority of international migrants move between countries of the ‘global south’ [ 2 ], these movements between low and middle-income countries remain a “blind spot” for policymakers, researchers and the media, with disproportionate political and policy attention focused on irregular migration to high-income countries. Migration is increasingly recognized as a determinant of health [ 3 , 4 , 5 ]. However, the bidirectional relationship between migration and health remains poorly understood, and action on migration and health remains limited, negatively impacting not only those who migrate but also sending, receiving, and ‘left-behind’ communities [ 1 ].

In February 2017, an international group of researchers participated in the 2nd Global Consultation on Migration and Health held in Colombo, Sri Lanka with the objectives of sharing lessons learned, good practices, and research in addressing the relationship between migration and health [ 1 ]. Hosted by the International Organization for Migration (IOM), the World Health Organization (WHO), and the Sri Lankan government, the Global Consultation brought together governments, civil society, international organizations, and academic representatives in order to address migration and health. The Consultation facilitated engagement with the health needs of migrants, reconciling the focus on long-term economic and structural migration - both within and across international borders - with that of acute, large-scale displacement flows that may include refugees, asylum seekers, internally displaced persons and undocumented migrants.

The Consultation was organised around inputs on three thematic areas: Global Health [ 6 ]; Vulnerability and Resilience [ 7 ]; and, Development [ 8 ]. These inputs guided working group discussions exploring either policy, research, or monitoring in relation to migration and health. This paper reports on the outcomes of the research group after an extensive period of debate at the Consultation and over the subsequent 9 months. We identify key issues that should guide research practice in the field of migration and health, and outline strategies to support the development of evidence-informed policies and practices at global, regional, national, and local levels [ 9 ]. Debate and discussion at the Consultation, and below, were guided by two key questions:

What are the opportunities and challenges, and the essential components associated with developing a research agenda on migration and health?

What values and approaches should guide the development of a national research agenda and data collection system on migration and health?

Our discussions emphasized that international targets, such as the Sustainable Development Goals (SDGs) and Universal Health Coverage (UHC; Health target 3.8 of the SDGs), are unlikely to be achieved if the dynamics of migration are not better understood and incorporated in policy and programming. To address this, and in order to improve policy and programming, a renewed focus on enhancing our understanding of the linkages between both international and internal migration and health, as well as the outcomes and impacts arising from them, is urgently needed.

Migration and health research: Leave no-one behind

The Sustainable Development Goals (SDGs) identify migration as both a catalyst and a driver for sustainable development. A clarion call of the SDGs is to ‘leave no-one behind’, irrespective of their legal status, in order to achieve Universal Health Coverage (UHC) for all [ 10 ]. In many countries, however, equitable access to health services is considered as a goal only in relation to citizens. Additionally, internal migration is left out of programming and policy interventions designed to support UHC for all. While UHC aims at ensuring “everyone” can access affordable health systems without increasing the risk of financial ruin or impoverishment, the formulation of UHC remains unclear regarding non-nationals/non-citizens [ 11 ]. While many international declarations state that the right to health applies to all, including migrants and non-citizens, many national policies exclude these groups in whole or part [ 12 ].

In addition to international and internal migration, the health concerns associated with labour migration require attention; migrant workers are estimated to account for 150.3 million of the 244 million international migrants [ 2 ]. While labour migration leads to significant economic gains for countries of origin and destination, true developmental benefits are only realised with access to safe, orderly and humane migration practice [ 13 ]. Many migrant labourers work in conditions of precarious employment, within ‘difficult, degrading and dangerous’ jobs yet little is known about the health status, health outcomes, and resilience/vulnerability trajectories of these migrant workers and their ‘left behind’ families. Many undergo health assessments as a pre-condition for travel and migration, yet many such programs remain unlinked to national public health systems [ 14 ].

Our discussions highlighted the complex and heterogeneous nature of research on migration and health, with particular concerns raised around the emphasis on international rather than internal migration, in view of the greater volume of the latter. The need for a multilevel research agenda to guide appropriate action on international and internal migration, health, and development was highlighted. In order to account for immediate, long-term and inter-generational impacts on health outcomes, migration and health research should: (1) incorporate the different phases of migration (Fig. 1 ); (2) adopt a life-course approach; and, (3) integrate a social determinants of health (SDH) approach.

Factors influencing health and wellbeing of migrants and their families along the phases of migration

Unease was expressed about the increasingly polarised political viewpoints on migration, often propagated by nationalist and populist movements, which present real challenges to researchers. This may also be associated with a reluctance to finance research exploring discriminatory policies that limit the access of international migrants to health services and other positive determinants of health, including work and housing.

The increasing complexity of global, regional, and national migration trends, as well as disagreements about the correct way to define and label different types of migrants, create additional difficulties within an already tense and politically contested research domain. Associated with this are the particular challenges associated with collecting and utilising data on ‘irregular migrants’ – international migrants currently without the documentation required to legally be in a particular country. These undocumented migrants, often living in the shadows of society, are more vulnerable to poor health outcomes due to restrictive policies on access to health and social services, to safe working and living conditions, and/or a reluctance to access services for fear of arrest, detention and/or deportation [ 15 , 16 ]. Whilst arguments for improving access to health care for marginalised migrants are based on principles of equity, public health, and human rights, the importance of research on the economic implications of limiting access to care for international migrants was highlighted [ 2 ]. This challenging terrain generated a myriad of research questions during the group discussions (Table 1 ).

Towards a framework for advancing migration and health research

The consultation took into account the extensive research experience of the group (see Appendix ), as well as engagement with key literature and context-specific evidence [see, for example 1–7]. Discussion led to the development of a framework that brings together what we identify as the key components for advancing a global, multi-level, migration and health research agenda (Fig. 2 ). Two areas of focus to advance the migration and health research agenda were identified: (1) exploring health issues across various migrant typologies , and (2) improving our understanding of the interactions between migration and health . Advancing research in both areas is essential if we are to improve our understanding of how to respond to the complex linkages between both international and internal migration and health. This, we argue, can be achieved by moving away from an approach that exceptionalises migration and migrants, to one that integrates migration into overall health systems research, design, and delivery, and conceptualises this as a way to support the achievement of good health for all.

Advancing Migration and Health Research at National, Regional and Global Levels: a conceptual framework

Building from these focus areas, our framework outlines the essential components for the development and application of multi-level research on migration and health. First are key principles underlying research practice: promoting interdisciplinary, human rights oriented, ethically sound approaches for working with migrants. Second are multi-level stewardship functions needed to meaningfully link migration and health research to policy practice and priority setting, [ 17 ]. This includes establishing knowledge exchange mechanisms, financing, commissioning, and utilising research to guide evidence informed policies. This may better enable health systems to become ‘migration aware’ [ 18 ] or what the International Organization for Migration (IOM) terms ‘mobility competent’ - sensitive to health and migration [ 1 ].

Migration and health research: Two key focus areas

Migrant typologies.

To assist in understanding the associations between migration and health, our research must find ways to better capture and engage with complex, dynamic, and often intersecting migrant typologies. We must be careful not to cluster migrants and their associated lived experiences, to simple, reductionist categories such as internal versus cross-border or documented versus undocumented, or even refugee versus economic migrant [ 19 ]. However, we do need a way of categorising different migrant groups when, for example, exploring epidemiological profiles and associated burdens of disease. To do this, we need to develop a set of nuanced yet flexible typologies that are able to capture the contextually relevant factors affecting migrant experiences, at both the individual and population levels. As outlined in Table 2 , this will require careful consideration of multiple factors to assist us in improving our understandings of the ways in which diverse migrant groups are associated, or not, with various health and wellbeing outcomes. Definitions that are based on immigration status - such as ‘refugee’, ‘immigrant’ or ‘asylum seeker’ - will incorporate diverse sub-groups, often with different levels of health vulnerabilities and resiliencies based on their migration trajectory. For instance, a refugee entering a country with an offer of permanent resettlement or with a recognized temporary protected status, will have different opportunities and challenges than an asylum-seeker, or migrant worker, crossing a border possibly without documents or a clear pathway to needed healthcare and protections. Each of these migrating populations carry different health burdens (and resiliencies) from their country of origin, their social position and access to resources, and their migration experiences; and each will face different barriers and uncertainties as they seek access to services, support and integrate in host communities. The definitions of migrant groups adopted by states not only need clear elucidation but also need to reflect the context-specific conditions affecting health access and protection. In Europe, for example, the entitlements to health care for asylum seekers differ by country [ 20 ]. The Migrant Integration Policy Index (MIPEX) health strand was developed as a tool to monitor policies affecting migrant integration in 38 different countries [ 18 ]. It measures the equitability of policies relating to four issues: migrants’ entitlements to health services; accessibility of health services for migrants; responsiveness to migrants’ needs; and measures to achieve change. Such tools are important steps in assessing migrant integration and for implementing migrant-sensitive policies that are aligned with the person-centred UHC principles.

An awareness of this complexity underlies the need to document multiple migrant voices and migration experiences along the diverse trajectories when exploring associations between migration and health. This could, for instance, involve capturing the voices of children and other family members ‘left-behind’ as a result of labour migration, or of seasonal migrant workers. Research into the issues, policies and programmes that influence health and health literacy among migrant populations and the role that communities, households, industries, schools, and transnational networks play in promoting health also needs exploration.

Key challenges exist when attempting to use and compare migration data internationally, as a result of differences in the definition of who is an international migrant, non-national, or internal migrant; inconsistent data sources; and limited data coverage. A recent analysis of the availability, reliability and comparability of data on international migration flows in European countries noted that “comparing migration flows in various countries would be like comparing pears and apples” [ 21 ]. The use of standard indicators can result in unreliable data if migration dynamics are not considered. For example, measures of life expectancy are skewed if international migrants return to their home countries when they are seriously ill, but their departure is not accounted for in vital registration or other systems [ 21 ]. Reporting that is based on incomplete, poor quality or non-comparable population data that fails to measure and/or report migration can give rise to misleading conclusions and limits the validity of data interpretation.

Research at the nexus of migration and health

We recognise the bi-directionality of the relationship between migration and health. Our research should explore how different forms of migration influence health – at both individual and population levels - and how health status affects decisions to migrate and shapes post-migration experience. Migration trajectories can positively or negatively impact health outcomes, just as health status can affect migration outcomes; this two-way relationship should be better reflected in research. To support this, we must be sure to differentiate carefully between different migrant typologies – for example within or across international borders and for what purpose: work, family reunification, escape from persecution, flight from conflict or natural disaster, or to seek asylum. Each of these operates within substantially different contexts whether one takes the migrant and their health into account, or their rights and entitlements, or how they are seen by the dominant society or community to which they migrate. We recognise that being a migrant is not in itself a risk to health: it is the conditions associated with migration that may increase vulnerability to poor health [ 4 ]. Owing to the ways in which people move and the spaces they traverse or at which they arrive, migrants may reside in - or pass through - ‘spaces of vulnerability’ [ 22 ] – key spaces associated with potentially negative health outcomes – including along transport corridors, urban slums, construction sites, commercial farms, fishing communities, mines, and detention centres. Such spaces may contain a combination of social, economic and physical conditions that may increase the likelihood of exposure to violence and abuse and/or acquisition of communicable or non-communicable disease [ 22 ]. The daily stressors that may be experienced in these spaces are increasingly acknowledged to affect emotional wellbeing and mental health [ 23 ].

As migration is an ever-changing dynamic process, generating and maintaining timely and comparable migration data and improving relevant information systems is important. ‘Quick wins’ in obtaining migration and health data by integrating migration variables into existing national demographic and health surveys, for instance, were highlighted. National disease control programs such as tuberculosis, HIV and malaria control programs should also be encouraged to collect data on internal and international migration, especially in cross-border areas. Communicable disease control remains a key health concern associated with human migration. Our discussions recognised the importance of embracing systems-theory approach for improving understanding of how migration influences not only disease transmission but also health promotion, and health-care seeking behaviours. The importance of collecting such data with strict adherence to research ethics and human rights was emphasised.

Towards a multilevel migration and health research agenda

To effectively inform policies and programs on migration and health, it is essential to invest in evidence generation through research at local, national, regional, and global levels. Identified approaches include the establishment of research reference groups at each level to support, guide, and connect the development and application of research to support evidence-informed policy making at multiple levels. Mapping and analysis of key stakeholders, migration patterns, existing legal frameworks, data source, and research output via bibliometric analysis is needed. Multi-level migration and health policy and priority setting processes must be guided by interdisciplinary and multisectoral thinking in order to address the multiple determinants associated with the health of both internal and cross-border migrants.

Key constituencies need to be mobilised from academia, civil society, international organizations, the private sector including employer groups, trade unions and migrant worker networks. These groups may also play a role in commissioning or directly undertaking applied research in order to advance better outcomes for migrants and communities in both places of origin and destination. High-level political leadership and health and development champions should raise the visibility of migration and health research. It is important to utilise existing research structures and resources to support the development of a research agenda on migration and health, as well as to seek support for the development of dedicated research commissions on migration and health at multiple levels in order to harness evidence to drive policy-making and programme formation. For instance, the Government of Sri Lanka, with the technical cooperation of IOM, commissioned a National Migration Health Research Study in 2010 to explore health impacts of inbound, outbound, and internal migrant flows including those of left-behind migrant families. The research findings ultimately contributed to the formulation of an evidence-informed National Migration Health Policy and national action plan in 2013 [ 24 ]. The research was led through local research institutions and research process were linked to an inter-ministerial and inter-agency process chaired by the Minister of Health. This evidence informed policy making process also led to a number of national programs such as ‘the national border health program’ in 2013, revitalizing domestic legal frameworks on health security, and advancing health protection of migrant workers at regional inter-governmental initiatives such as the Colombo Process.

At the regional level, consultative processes are required to develop common approaches to migration and health, including communicable disease surveillance, monitoring of interventions, applied research collaboration across national borders and capacity building – particularly interdisciplinary postgraduate training. For instance, the Mekong Basin Disease Surveillance (MBDS) Consortium is a sub-regional co-operation spearheaded by health ministries from member countries Cambodia, China, Lao PDR, Myanmar, Thailand and Vietnam [ 25 ]. In relation to labour migration, regional processes – such as the Colombo Process [ 26 ] - should explore the management of overseas employment and contractual labour. In addition, migrant health-related concerns should be emphasised in the negotiation of free trade agreements that increase migration between states, such as the Post-2015 Health Development Agenda for a “ Healthy, Caring and Sustainable Community ” initiative of the Association of South-East Asian Nations (ASEAN) [ 27 ] and efforts to implement the “Health in all Policies” strategy of the European Union [ 7 ].

Methods to map human mobility for public health preparedness and response stemming from outbreaks and other health emergencies are needed in order to provide accurate information on population movements, for monitoring the progression of outbreaks, predicting future spread and allocating resources for surveillance and containment strategies. Human mobility was a critical factor in the spread of Ebola virus in the West African region.

A coordinated global research agenda on migration and health is urgently needed. Potential elements include collaboration with stakeholders involved in implementing global initiatives – such as the SDGs – to ensure that indicators and data collection strategies are sensitive to both internal and cross-border migration, and health related issues. Identification of datasets and data collection processes that can be adapted and mined for disaggregated health data related to migration are also crucial in advancing the evidence base. We support the development of a sustainable global reference group that can share research evidence, expertise and experience, develop methodological and ethical guidelines, undertake multi-country studies, provide training and build a global knowledge hub in migration and health. Such a group can also mobilise funders and development partners, collaborate with scientific and professional associations, and engage with journals and publishers to create awareness on the need to better promote migration and health research.

The ‘Migration, Health, and Development Research Initiative’ (MHADRI) is a global network of academics and other research partners who aim to advance migration and health research practice [ 28 ]. The research network was formed around the need to build a global alliance of migration and health researchers and provide a platform to share, collaborate, develop, mentor, advocate and disseminate inter-disciplinary research at the nexus of health and migration. A key goal of the network is to enable researchers from developing nations the opportunity to collaborate and promote research in the Global South. The network has grown to encompass 100 researchers globally, across diverse disciplines, geographic areas and stages of career. A global reference group would be well placed to develop good practice guides on data collection systems, research methods and ethics; research translation and dissemination; and, policy integration strategies.

Research principles

We identified core principles that should guide research on migration and health, and work with migrant populations: an ethically sound human rights approach to research that involves engagement across multiple disciplines. Researchers need to be sensitive when designing and disseminating research findings as data on migration and health may be misused, both at an individual and population level. Key questions related to how researchers can exercise their duty of care as they engage in research, and how we can promote careful use of data and research to make sure it does more good than harm. Activities associated with international migration sometimes take place in a climate of victim blaming, othering, and stigmatisation that prioritises purported national security concerns [ 29 ]. Pressing concerns were identified that relate to the ways in which researchers can navigate this increasingly challenging environment, and how trust can be established among different stakeholders – including with international migrant groups. Securitization agendas also affect the health of migrants by excluding, discriminating and/or blaming migrants as vectors of disease. Ethical approaches to research, with a clear commitment to universal human rights, are therefore paramount in a climate of increasingly restrictive immigration regimes.

Discussions also highlighted the challenges associated with the collection of data with and from migrant populations. These include sampling, biases, and practical barriers such as language and culture, as well as the challenges inherent in reaching people who are often highly marginalised and potentially criminalised. Particular attention needs to be given to ethical issues: protecting confidentiality and ensuring that participation in research does not have an adverse impact on migrants, especially irregular migrants, and that participants gain access to relevant services if required. The development of meaningful partnerships and respectful research practice with actors involved in the migration process will also improve the quality, reliability, legitimacy, and use of the data generated.

Contributions from a range of disciplines – such as anthropology, demography, sociology, law, political science, psychology, policy analysis, public health, and epidemiology – are required to unpack the complex relationships between migration and health. Approaches to “slow research” [ 30 ] may help increase the sensitivity of epistemologies and methods to local realities, intricate dynamics, and the multiple voices and perceptions of migrants, health professionals and other individuals involved [ 24 ]. However, the lack of dedicated research units, institutes or centres on migration and health - especially within lower-income country contexts - require existing researchers and scholars to consolidate and better engage with sub-regional, regional and global research networks to ensure capacity building, mentoring, and support. Sensitising the donor community to the migration and health agenda, especially those funding research, is paramount. Curriculum development and teaching support for building the next generation of migration and health researchers is critical to successfully building and sustaining future research on migration and health.

Stewardship elements

We discussed the importance of developing appropriate research translation and engagement activities in order to support key, identified stewardship functions [ 17 ] at the global, regional, national and local levels. Key gaps in stewardship related to the lack of major funding mechanisms for research at national, regional, and global levels, and the need to invest in capacity building for emerging researchers through training programs and support, especially for researchers in lower-income country settings. Collaboration is required to support relationships among researchers and with relevant stakeholders, particularly with migrant communities. This includes building inclusive migration and health research networks, developing communities of practice, and supporting collaborations with those working on other global health priorities. Our research also needs to include the experiences of service providers who engage with various migrant populations, such as those within the health care sectors, border management, law enforcement, and labour migration. The development of effective research translation and public engagement strategies for sharing research findings is critical: not only to shape multi-level policy processes but also public and political opinion.

There was clear consensus on our commitment to enhancing the quality and breadth of multi-level research evidence to support the development of improved responses to migration and health. The importance of an ‘enabling environment’ for migration and health research at local, national, regional and global levels was emphasised, as was the development of meaningful linkages – such as through research reference groups – to support evidence-informed and intersectoral policy and priority setting processes. Our research needs to be underpinned by a human rights approach to health and sound ethical practice. With adequate funding, capacity development, and support for academic freedom, we can improve the evidence base to guide policy and programming for migration and health at multiple levels and in so doing contribute to improving health for all.

Abbreviations

Association of South-East Asian Nations

International Organization for Migration, the UN Migration Agency

Mekong Basin Disease Surveillance

Migration, Health, and Development Research Initiative

Sustainable Development Goals

World Health Organization

IOM. Health of migrants: resetting the agenda. Report of the 2nd global consultation. Colombo, Sri Lanka, 21-23 February 2017. Geneva: IOM; 2017. https://www.iom.int/sites/default/files/our_work/DMM/Migration-Health/GC2_SriLanka_Report_2017_FINAL_22.09.2017_Internet.pdf

Google Scholar  

IOM. Global Migration Trends Factsheet. Berlin: Global Migration Data Analysis Centre, IOM; 2017. http://gmdac.iom.int/global-migration-trends-factsheet . Accessed 13 Sep 2017.

Castañeda H, Holmes SM, Madrigal DS, Young M-ED, Beyeler N, Quesada J. Immigration as a social determinant of health. Annu Rev Public Health. 2015;36:375–92.

Article   PubMed   Google Scholar  

Davies A, Basten A, Frattini C. Migration: a social determinant of migrants’ health. Migr Health Eur Union. 2010;16:10–2.

Chung RY, Griffiths SM. Migration and health in the world: a global public health perspective. Public Health. 2018;158:64–5.

Article   PubMed   CAS   Google Scholar  

IOM. Global Health - Thematic Discussion Paper. Geneva: IOM; 2017. https://www.iom.int/sites/default/files/our_work/DMM/Migration-Health/GC2_TDP_Global%20Health_FINAL_13.02.2017.pdf . Accessed 13 Sep 2017.

IOM. Vulnerability and Resilience - Thematic Discussion Paper. Geneva: IOM; 2017. https://www.iom.int/sites/default/files/our_work/DMM/Migration-Health/GC2_TDP_Vulnerability-and-Resilience_FINAL_13.02.2017.pdf . Accessed 13 Sep 2017.

IOM. Development - Thematic Discussion Paper. Geneva: IOM; 2017. https://www.iom.int/sites/default/files/our_work/DMM/Migration-Health/GC2_TDP_Development_FINAL_13.02.2017.pdf . Accessed 13 Sep 2017.

Bowen S, Zwi AB. Pathways to “evidence-informed” policy and practice: a framework for action. PLoS Med. 2005;2:e166.

Article   PubMed   PubMed Central   Google Scholar  

United Nations General Assembly: Transforming our world: the 2030 agenda for sustainable development, Resolution RES/70/1. New York; 2015.

Lougarre C. Using the right to health to promote universal health coverage. Health Hum Rights. 2016;18:35–48.

PubMed   PubMed Central   Google Scholar  

Abubakar I, Devakumar D, Madise N, Sammonds P, Groce N, Zimmerman C, et al. UCL–Lancet Commission on migration and health. Lancet. 2016;388:1141–2.

IOM. World Migration Report 2018. Geneva: IOM; 2018. https://publications.iom.int/system/files/pdf/wmr_2018_en.pdf . Accessed 2 July 2018

Wickramage K, Mosca D. Can migration health assessments become a mechanism for global public health good? Int J Environ Res Public Health. 2014;11:9954–63.

The Lancet. Adapting to migration as a planetary force. Lancet. 2015;386:1013.

Article   Google Scholar  

Willen SS, Knipper M, Abadía-Barrero CE, Davidovitch N. Syndemic vulnerability and the right to health. Lancet. 2017;389:964–77.

Saltman RB, Ferroussier-Davis O. The concept of stewardship in health policy. Bull World Health Organ. 2000;78:732–9.

PubMed   PubMed Central   CAS   Google Scholar  

Vearey J. Mobility, migration and generalised HIV epidemics: a focus on sub-Saharan Africa. In: Thomas F, editor. Handbook on Migration and Health: Edward Elgar Publishing, United Kingdom; 2016.

Hanefeld J, Vearey J, Lunt N, Bell S, Blanchet K, Duclos D, et al. A global research agenda on migration, mobility, and health. Lancet. 2017;389:2358–9.

IOM. Summary Report on the MIPEX Health Strand and Country Reports. Geneva: IOM; 2016.

Kupiszewska D, Kupiszewski M, Martí M, Ródenas C. Possibilities and limitations of comparative quantitative research on international migration flows. Brussels: European Commission; 2010.

Crush J (Ed. Spaces of Vulnerability: Migration and HIV/AIDS in South Africa (Migration Policy Series No. 24). 2002.

Vearey J. Healthy migration: a public health and development imperative for south(ern) Africa. S Afr Med J. 2014;104:663.

Wickramage K, Mosca D, Peiris D, Wickramage K, Mosca D, Peiris S, editors. Migration health research to advance evidence based policy and practice in Sri Lanka volume 1. Philippines: Institute of Medicine, 2017. Phillipines: Institute of Medicine; 2017.

Phommasack B, Jiraphongsa C, Ko Oo M, Bond KC, Phaholyothin N, Suphanchaimat R, et al. Mekong Basin disease surveillance (MBDS): a trust-based network. Emerg Health Threats J. 2013;6 https://doi.org/10.3402/ehtj.v6i0.19944 .

The Colombo Process Portal. http://colomboprocess.org /.

AESAN. ASEAN Post-2015 health development agenda. ASEAN; 2017. http://asean.org/storage/2017/02/APHDA-In-a-Nutshell.pdf . Accessed 13 Sep 2017.

Migration Health Research Portal. https://migrationhealthresearch.iom.int/mhadri . Accessed 13 Sept 2017.

Grove NJ, Zwi AB. Our health and theirs: forced migration, othering, and public health. Soc Sci Med. 2006;62:1931–42.

Adams V, Burke NJ, Whitmarsh I. Slow research: thoughts for a movement in Global Health. Med Anthropol. 2014;33:179–97.

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Acknowledgements

Members of the research stream at the 2nd Global Consultation on Migration and Health who participated and contributed to the discussions (see Appendix ).

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Contributions

All authors contributed to structuring and facilitating the research stream at the Global Consultation. KW, JV, AZ, CR, MK documented and synthesized the key themes emergent from the working groups and prepared ‘mind maps’. KW authored a section in the final report from the Global Consultation on behalf of the research stream, on which this article is based. JV wrote first draft of the article. KW and JV revised the article based on very helpful comments from two reviewers. All authors reviewed and approved the final manuscript.

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Members of the research stream at the 2nd Global Consultation on Migration and Health

In alphabetical order:

Ibrahim Abubakar (Director, Institute for Global Health, University College London, United Kingdom)

Anjali Borhade (Associate Professor, Indian Institute of Public Health, India)

Chee-khoon Chan (Research Associate, University of Malaya, Malaysia)

Julia Puebla Fortier (Executive Director, Diversity Rx - Resources for Cross Cultural Health Care)

Charles Hui (Associate Professor of Paediatrics and Chief of Infectious Diseases, University of Ottawa, Ottawa, Ontario)

Michael Knipper (Associate Professor, Institute of the History of Medicine of the University of Giessen, Germany)

Michela Martini (Migration Health Regional Specialist, IOM Regional Office for Horn, East and Southern Africa, Nairobi, Kenya)

Moeketsi Modisenyane, National Department of Health, South Africa

Davide Mosca (Director, Migration Health Division, IOM, Geneva, Switzerland)

Kevin Pottie (Associate Professor, Faculty of Medicine, University of Ottawa, Ottawa, Ontario)

Bayard Roberts (Director, The Centre for Health and Social Change at the London School of Hygiene and Tropical Medicine, London, United Kingdom)

William Courtland Robinson (Associate Professor, Johns Hopkins Bloomberg, School of Public Health, USA)

Chesmal Siriwardhana (Associate Professor, London School for Hygiene and Tropical Medicine)

Ursula Trummer (Head, Center for Health and Migration, Vienna, Austria)

Jo Vearey (Associate Professor, African Centre for Migration & Society (ACMS), University of the Witwatersrand)

Kolitha Wickramage (Migration Health and Epidemiology Coordinator, IOM, Manila, Philippines)

Anthony Zwi (Professor of Global Health and Development, The University of New South Wales, Sydney, Australia)

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Measuring migration 2.0: a review of digital data sources

• Jasper Tjaden   ORCID: orcid.org/0000-0002-5054-3535 1 , 2  

Comparative Migration Studies volume  9 , Article number:  59 ( 2021 ) Cite this article

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The interest in human migration is at its all-time high, yet data to measure migration is notoriously limited. “Big data” or “digital trace data” have emerged as new sources of migration measurement complementing ‘traditional’ census, administrative and survey data. This paper reviews the strengths and weaknesses of eight novel, digital data sources along five domains: reliability, validity, scope, access and ethics. The review highlights the opportunities for migration scholars but also stresses the ethical and empirical challenges. This review intends to be of service to researchers and policy analysts alike and help them navigate this new and increasingly complex field.

Introduction

International interest in measuring human migration is at an all-time high. The number of people living in a country other than their country of birth reached an estimated 272 million in 2019, an increase of 51 million from 2010 (UN DESA, 2019 ). The number of forcibly displaced people due to conflicts and disasters is at its historic high (UNHCR 2020 ). International migration is expected to continue increasing given higher levels of interconnectedness in the world due to improved communication and transport systems, protracted crises producing displacement, and structural changes such as climate change and population growth in certain world regions.

Governments worldwide have a keen interest in anticipating future migration flows and understanding the drivers of migration to plan ahead, allocate funds, attract workers and students, use remittances, facilitate migrant integration, and manage public opinion, among other issues. The increased demand for systematic measurement from policymakers has also manifested itself in two landmark policy frameworks adopted in the last decade: The Global Compact on Migration (GCM) and the Sustainable Development Goals. Footnote 1

Second, in step with the increased salience of migration in policy circles, migration research output has grown dramatically (Pisarevskaya et al., 2019 ). Between 1960 and 1980, the number of academic journals on related subjects quadrupled. In 2020, the International Organization for Migration (IOM) identified over 130 migration-related journals publishing more than 2000 journal articles in English, French or Spanish (IOM, 2020 ).

Policy and scholarly interest both rely on fundamental measurements of migration, i.e. how many people migrate (flows) or have migrated (stocks) within a specific time frame. Yet, the popularity and relevance of migration has outpaced substantial improvements in the systematic measurement of migration, especially at the global level. Indeed, the demand for ‘evidence’ has revived long-standing calls for better data on international migration which experts have been lamenting for decades (Bilsborrow et al., 1997 ; Clemens et al., 2009 ; Laczko, 2016 ; Lemaitre, 2005 ; Willekens et al., 2017 ). Footnote 2

This is the context in which a set of new data sources emerged providing migration researchers of all disciplines with new opportunities to measure migration. The arrival of “innovative data sources”—often referred to as “Big Data” or “digital trace data”—have been described as a “migration data revolution” (Laczko & Rango, 2014 ) and bears much potential to complement traditional migration data (Cesare et al., 2018 ; Sîrbu et al., 2021). At the same time, digital data present a host of new ethical challenges for researchers that are of great concern (Beduschi, 2020 ; Brayne, 2018 ; Hayes, 2017 ; Latonero & Kift, 2018 ; Leese et al., 2021 ; Molnar, 2019 ; Zwitter, 2014 ).

As new researchers and policymakers flock to the field of migration and the empirical study of migration diversifies, there is a need to explain and review new migration data sources to provide a better understanding of their respective limitations and strengths. This paper reviews eight data sources in terms of their reliability, validity, scope for research, access and ethics. The aim is to familiarize experienced and incoming migration scholars with new approaches. The review should be considered an attempt to contribute towards a broader process of interdisciplinary dialogue and expanding the empirical toolbox in migration studies.

Analytical framework

Defining migration.

Before mapping novel data sources, it is important to first define migration for the purpose of this study and clearly delineate the scope of the review.

Important aspects of definitions of migration are space (internal or domestic vs. international/ cross-border migration), time (short term vs. long term), type (e.g. labour, irregular, forced, family, education) and form (flows vs. stocks) (Bilsborrow, 2016 ; UN DESA, 2017 ). This review takes a broad and inclusive view in line with its aim to describe a menu of novel data sources for diverse groups of migration scholars and research interests. Here, migration will be defined as the changing of residence of an individual within or outside the boundaries of a country for longer than three months. While this definition is broad, it excludes certain types of mobility such as travel for the purpose of recreation, holiday, visits to friends or relatives, business, medical treatment or religious pilgrimage (which usually do not imply a change of residence). Footnote 3 The review considers data sources providing information on both migration flows (i.e. the number of migrants entering and leaving (inflow and outflow) a country over the course of a specific period, for example, one year) and migration stocks (i.e. the total number of migrants present in a given location at a particular point in time) (see Global Migration Group, 2017 ). The review considers any form and channel of migration including, among others, labour, family, forced and irregular migration and is not restricted geographically. In addition, to actual observed migration, the review also considers proxies for migration; such as, migration intentions, plans, desires, or aspirations that are commonly used to predict a future change of residence (Tjaden et al., 2019 ). Footnote 4  The review does not include how novel data can be used to research other fields of interest to migration scholars such as integration, the causes of migration, communication, or the impact of migration on society. These fields are not primarily concerned with or rely on (directly or indirectly) inferring migration flows or stocks from data.

Defining “novel” data sources

What are these “new” data sources and what makes them “newer” than the “old” sources? Two popular concepts are helpful to delineate traditional from “innovative” data sources for migration: “big data” and “digital trace data”.

Big data is commonly defined by the “three V’s”: volume, velocity, variety. Volume refers to the magnitude of data. However, there is “little consensus around the fundamental question of how big the data has to be to qualify as “big data” (Gandomi & Haider, 2015 : 137). Velocity refers to the rate at which data are generated which has dramatically increased with the proliferation of digital devices such as smartphones and sensors. Variety refers to the type of data that is being generated. Big data often includes numerical data, text data, images, audio and geo-location data. These Vs are useful to describe many of the sources that are commonly associated with big data such as social media platforms (Facebook, Twitter, Twitter, Instagram etc.) and online search platforms (google). These data compile millions of records about their users ranging from location, online activity to demographic user profile information. At the same time, this information is accessible in real-time, sometimes even publicly through application programming interfaces (APIs). “Big data” includes social media data but is not limited to it. Google, for example, offers a search service which does not operate as a social platform.

Digital trace data are the “results of social interaction via digital tools and spaces as well as digital records of other culturally relevant materials, such as archived newspapers and Google searches including data from popular social networking sites (such as Facebook or Twitter), personal blogs, collaborative online spaces (such as Wikipedia), and data derived from mobile phone or credit card usage” (Cesare et al., 2018 : 1980).

The terms “big data” and “digital trace data” refer largely to the same type of sources. However, while term “big data” highlights the type of data that is produced, the term “digital trace” data focuses on how the data is produced, i.e. through using digital devices (Cesare et al., 2018 ; Hughes et al., 2016 ; Sîrbu et al., 2020 ).

New data sources are often collected by private companies for the purpose of offering services to customers. In contrast, “traditional” sources of migration data such as censuses, administrative data and surveys are traditionally collected or made available by government agencies or (publicly funded) research institutes. Footnote 5 This has far-reaching ethical and empirical implications which will be discussed in later sections.

Review criteria

The review will discuss new data sources along five domains: (1) Reliability—the consistency and reproducibility of migration measurements, (2) validity—the accuracy of migration measures and the extent to which data allows to capture the intended concepts used by migration researchers, (3) scope—the breadth and depth of migration-related research that could be explored based on the respective data source, (4) accessibility—the degree to which data is accessible to researchers, and lastly, (5) ethics –the potential risk of violations of data privacy, consent and data protection principles in the data generation process and potential risk of (unintended) harm for research subjects as a result of analysis produced based on new data sources (e.g. Beduschi, 2020 ; Brayne, 2018 ; Cesare et al., 2018 ; Hayes, 2017 ; Latonero & Kift, 2018 ; Leese et al., 2021 ; Molnar, 2019 ; Zwitter, 2014 ).

Review of innovative data sources to measure migration

Mobile phones: call detail records and gps data from smartphone operating systems.

Mobile phone Call Detail Records (CDR) can track the approximate location of individuals and, as a result, display movements across space by capturing the call signal sent to cell towers for each outgoing and incoming call (Williams et al., 2015 ). All caller details are anonymized. Some telecommunications providers are amenable to social research as well, and often provide documented and anonymized digital trace data from their customers to researchers interested in analysing these data (e.g. Cesare et al., 2018 ; Chi et al., 2020 ).

Reliability CDR provides reliable measures of migration in terms of consistency over time. Movements are recorded automatically as required by operating the telephone network. An advantage in terms of reliability is that the information on location does not rely on self-reports by individuals, which may be subject to response biases (a common issue in surveys). However, reliability issues may apply when using CDR data from different operators. This is a common issue because most countries have several telecommunication companies. As consumers switch services, measures of movement over time become less reliable. As a result, CDR is often used on narrowly defined locations and limited time frames.

Validity The key disadvantage is that such data refers to mobile devices, not individuals as such. It is possible that individuals will share the same device, or gift it to others. Furthermore, many migrants may change devices and/or SIM cards after migrating to other countries, given that service providers offer deals limited to particular countries. Therefore, most contributions using phone data have analysed mobility within narrow geographic units (cities, regions) rather than movements across borders. Furthermore, CDRs can be biased because locations are only recorded when calls are made leaving blank spots in the migration process. Footnote 6

Scope While CDR data are usually more helpful for identifying internal (sub-national) migration patterns, Footnote 7 in some cases they can also be used to measure international migration at the sub-regional level, particularly when combined with other sources. For example, CDR have been used to track internal displacement following natural disasters such as the Haiti and Nepal earthquakes (Bengtsson et al., 2011 ), and the combination of CDR with satellite data can help to map movements between cross-border communities (Hughes et al., 2016 ). Recent work has leveraged Google Location History data for analysis on migration flows. Google Location History is collected through smartphones that operate the Google Android system and through Google services used through smartphones (e.g. Google Maps or Gmail). Pilot research suggests that this novel source of information could provide information about international migration through ‘fine scale mobility with rare, long distance and international trips’ documented through changes in location by users (Ruktanonchai et al., 2018 ). Using the same data, Kraemer et al. ( 2020 ) described ‘global human mobility patterns, aggregated from over 300 million smartphone users’. According to the authors, the data cover nearly all countries and 65% of earth’s populated surface, including cross-border movements and international migration. The advantage of CDR and location data through smartphone use for measuring migration is the timeliness and detail regarding the location. As such, phone records are particularly useful for studying sudden movements in defined geographic locations. Fast evolving migration situations are difficult to capture with “traditional” data sources such as sample surveys and administrative data, and impossible using censuses.

Without linking mobile phone records to other data sources, CDR provides a limited scope for migration scholars. The only information available is time and location. The type, channel and motivation for a change in location remains unobserved. It thus remains unclear who moved, why people moved, where they wanted to go, who they travelled with, through which channel they travelled, and whether they are likely to stay in their current location. This lack of context information is a key shortcoming compared to “traditional” sample survey research.

Accessibility CDR data is not commonly available to researchers and access depends on willingness of telecommunication companies to collaborate. Different operators in different countries may need to comply with different data protection legislation limiting the extent and level of detail of data that can be shared. In addition, access is often tied to large fees.

Ethics CDR data poses serious ethical concerns. When entering a mobile phone contract or installing a smartphone operating system, many users may not be aware that their location data is collected and analysed for various purposes (Beduschi, 2020 ; Brayne, 2018 ; Molnar, 2019 ). Such data uses are often hidden in the fine print. Since telecommunication and smartphone operating system providers are often private companies, there is a lack of transparency of what companies do with the data. In many countries, governments can mandate companies to provide access to data, for example, for the purpose of criminal investigations (Brayne, 2018 ). In the field of migration, the granular CDR data can be used to target humanitarian assistance to specific populations in specific locations, however, it could also be used by authorities for enforcing immigration policies, border protection and identifying individuals entering or residing in a country with an irregular status.

Social media

Geo-located social media activity, such as activity on Facebook (Zagheni et al., 2017 ), Twitter (Chi et al., 2020 ; Fiori et al., 2017 ; Martin et al., 2020 ; UN Global Pulse, 2017 ; Zagheni et al., 2014 ), Skype (Kikas et al., 2015 ), or LinkedIn (State et al., 2014 ), have been used to infer migration flows and stocks based on the location where users log in or information on location provided by the users themselves through geo-tagged posts or profile information (e.g. nationality or birthplace).

Movement is usually inferred based on changes users make to their self-reported location on the respective platform, or changes in location of log-ins. For example, data from the Facebook advertising platform can yield information on ‘home country’ and country of current residence. This means that Facebook could be used as a ‘real-time census’ to estimate, among other things, the number of users classified by the social media platform as ‘expats’ (users living in a country other than their ‘home country’) at the national or global level at a certain point in time (Zagheni et al., 2017 ). Using changes in Facebook users’ locations over time, others have identified the increase in the number of Venezuelan migrants in Spain in early 2018, confirmed by official statistics from the Spanish National Statistical Office (Spyratos et al., 2019 ).

Reliability There are a host of reliability concerns involved in measuring migration using social media data. First, certain segments of the population may be over- or under-represented (for instance, on average, young people are more likely to use Facebook than older people). Footnote 8 Second, even frequent users may choose not to provide information on their past and current location. Certain types of migrants may deliberately avoid providing information on their location on social networks. Third, it is difficult to verify whether changes in location are accurate, given that this information is sometimes self-reported on a voluntary basis. Fourth, the user base of social media providers constantly changes, which complicates analysis of trends over time (see e.g. Cesare et al., 2018 ).

Validity With many kinds of social media data, there is a lack of transparency on key measures relevant for migration are generated. For example, there is limited information on how Facebook identifies who is an “expat” or how it labels users as speakers of a different language. This complicates meaningful interpretation of migration patterns observable in the data.

Scope The advantage of geo-located social media data is that, in many countries, certain social media platforms are wildly popular, so that real-time data on large volumes of movements can potentially be accessed. Such data may be particularly useful to study broader migration trends. The level of detail provided by geo-coded social media data is limited in many cases but more extensive compared to CDR data. For example, Facebook provides aggregate-level information on the number of users with specific characteristics such as age, gender, or even education and income proxies as well as a vast range of preferences (measured via users’ “likes” of particular pages). Changes in the characteristics of the number of people living in a specific place are used by researchers to infer ‘migration flows’, assuming that changes in the ‘stock’ of people that report that they live somewhere necessitates that people moves from countries with lower stock numbers to countries with higher stock numbers. Information on friendship networks across countries—recently made available by Facebook—may be used in the future to forecast cross-country migration trends (Tjaden et al., 2021 ). Despite availability of additional characteristics, the data provide no information about the causes, means, or consequences of migration. There are attempts by governments, law enforcement agencies, international organization and research institutes to monitor the social media activity of migrants before, during and after migration to understand changes in migration patterns (Brenner & Frouws, 2019 ; Dekker et al., 2018 ; Sanchez et al., 2018 ). Footnote 9

Access Many social media companies offer public APIs to allow access to certain parts of their data to researchers. In many cases (e.g. Facebook, Twitter), access can be obtained at no cost which is a substantial advantage over traditional sources such as censuses, administrative data and survey. However, access modalities can change at any given time because data is provided by private companies, rather than taxpayer-funded government or research bodies that are mandated to provide systematic data over time.

Ethics Users of social media are often unaware of the data that is being collected about them and there is a general lack of understanding how such data is and can be used by companies themselves or third parties (Cesare et al., 2018 ; Zwitter, 2014 ). Migration enforcement agencies may use such data for surveillance purposes, which are particularly serious in contexts of irregular migration and forced displacement. Agencies could monitor communication of specific groups or individuals on Twitter and Facebook to identify irregular migrants and track them during their journeys. Companies such as Facebook, however, only allow access to anonymized, aggregate level data to researchers which limits the possibility of using data to harm individuals. Any information on narrowly defined locations and groups becomes inaccessible if the underlying target population decreases beyond a threshold that risks identifying any specific individuals. However, this does not apply to attempts to monitor public communication in social media groups indicating changes in migration patterns. The European Asylum Support Office (EASO) has suspended its efforts to monitor communication of migrants on social media following concerns by the EU own data protection body. Footnote 10

Email IP addresses

Repeated logins to the same website and IP addresses from e-mail activity have also been used to estimate international mobility patterns and users’ likelihood to move to another country (Zagheni & Weber, 2012 ). Rather than self-reported location by the user, certain online services such as email providers collect data on where users log into their accounts.

Reliability and validity The same limitation in terms of reliability and validity apply compared to social media data. Similar to log-ins to social media, log-ins to emails are usually recorded via devices (IP addresses) not necessarily people. For example, it is possible—yet presumably rare—that various people use the same email account which will distort any aggregate measure of migration.

Scope The scope of potential migration analysis is further reduced in the case of email log-ins given that additional socio-demographic and socio-economic information about the users (which are available for Facebook) is lacking or not publicly accessible.

Access Most email providers also do not provide public APIs that make data available to researchers. Email communication is considered personal and private communication whereas some communication on social media platforms is (intentionally or unintentionally) made public by users.

Ethics Similar to social media data, there are issues concerning consent and data privacy. Users may not be aware that email providers track their location. In other cases, governmental enforcement agencies may mandate companies to share content of emails of specific individuals for the purpose of criminal investigations or intelligence which bears the potential for misuse also in case of migrants in irregular settings (Brayne, 2018 ).

Online search data

Online search data has also been used more recently to study migration. Records on Google searchers, for example, have been explored to forecast the number of arrivals of asylum-seekers in Europe (Connor 2017) or internal migration within the U.S. (Lin et al., 2019 ). Search data generated through Google’s online search platform for migration can be exploited to measure migration intentions and predict subsequent emigration flows (Böhme et al., 2018 ; UN Global Pulse, 2014 ). For example, researchers retrieve data on how many times individuals in country A have ‘googled’ a term that the researcher believes to indicate an intention to migrate (to country B)—for example, ‘jobs’, ‘visa’, or the name of the destination country.

Reliability Google Searches are recorded consistently and provide high reliability in terms of the measure as such. The main advantage to Search Data is that Google’s search engine is widely used across the globe and has been successfully used to study other social behaviours (e.g. flu outbreaks). Despite broad coverage, important countries (i.e. China) are missing entirely. Issues of reliability emerge regarding applicability across various country contexts, languages and specific populations. Preliminary research in this area suggests that online searches (e.g. via Goole searchers) are related to actual movement at the aggregate level, yet the selection of specific search terms in various country contexts appears to be highly important. Syrians looking for ways to flee to Europe ‘google’ different terms than Canadians looking for a job in the US. The meaning of the same search terms may also vary in different languages. Overall, this means that Google searches may be indicative of migration from a certain country to another country, but difficult to scale up to multiple migration contexts (see Tjaden et al., 2021 ).

Validity Online search data has one obvious shortcoming: ‘searching’ is not ‘doing’. Just because someone looks up information on another country or, more explicitly, gathers information on how to move to another country, does not mean that they will actually move. Search data (similarly to survey data on emigration intentions) are a ‘pre-behavioural’ proxy for actual migration. Some studies suggest that intentions are a good predictor for eventual migration (Van Dalen & Henkens, 2013 ; Tjaden et al., 2019 ), but research also suggests that the strength of the predictor varies considerably based on where migrants are from and where they want to go (Tjaden et al., 2019 ).

Scope A major disadvantage of Google search data is the high level of aggregation at which data is made available. Search data is made available at the population level for countries or, in certain countries like the US, for subregions. Search data does not include any additional information about those who show interest in migrating, and thus renders any individual-level analysis impossible.

Access Google search data is freely and publicly accessible via the Google Trends platform and API.

Ethics The potential risk of misuse of data is limited given the high level of aggregation and anonymity of data which the company makes available. Serious concerns would arise when data for specific locations and IP addresses is used to infer individual level migration behaviour. Google itself is analysing individual-level location data to provide targeted advertisements to users who use their search engine. However, there is a lack of transparency in terms of the conditions under which such data may be shared with governments or other third parties. In addition, usual concerns around unawareness among users about the usage of their data apply.

Bibliometric data

Bibliometrics is a field of research that uses statistical methods to systematically analyse publications records (books, articles etc.). One sub-field of bibliometrics—scientometrics—is the analysis of scientific publications. Detailed information about academic output is recorded and made accessible through scientific databases (e.g. Scopus, Web of Science, Google scholar and others). This information has been used to model the international mobility of academics (Czaika & Orazbayev, 2018 ; Laudel, 2003 ; Moed & Halevi, 2014 ; Sudakova & Tarasyev, 2019 ; Wang et al., 2019 ). Changes in the researchers’ affiliation to institutions located in different countries indicates migration.

Reliability Measuring migration through changes in affiliations is consistent and reliable. Scientists have an interest to publish their work in recognized journals and books, institutions have an interest that researchers indicate their home institution, and most research outlets make it mandatory for authors to provide this information. Nevertheless, the data is sensitive to the accuracy of self-reported data which can be outdated.

Validity Migration analysis based on bibliometric data has the potential to collect additional context information including socio-demographic characteristics of the professionals (age, gender, ethnic origin, for example, may be inferred based on name recognition algorithms and web scraping individual professionals’ web pages). Additional information about the universities, faculty and chair may be matched with additional effort.

Scope The drawback of this data source is its restriction to a narrowly defined group of professionals (i.e. academics) where public access to their affiliation is the norm. However, it may be possible to extend this approach to other fields of professionals where public information on affiliations is common (i.e. athletes, musicians etc.).

Access Bibliographic data has become available through the digitalization of entire libraries, records of publishers, academic journals, and ambitious projects such as Google Books and Google Scholar that aim to record any academic publications that is published. Most academics provide their affiliations publicly to gain visibility and broaden their reach.

Ethics Compared to previously described sources, ethical concerns are limited because the personal information used for analysis is provided voluntarily and knowingly. The population is restricted to regular labour migrants which limits the potential for misuse by authorities.

Remote sensing technologies

Remote sensing is an umbrella term for collecting information about something without making physical contact. In current usage, remote sensing refers to the use of satellite or aircraft-based sensor technologies (i.e. drones). Remote sensing is commonly used in geography, earth sciences, climate research, agricultural studies, wildlife studies, military, and intelligence gathering, but also increasingly for urban planning, tourism, commerce, and various humanitarian applications (Miller et al., 2019 ). Changes in human activity visible in the images (i.e. settlements, refugee camps, light emissions at night) can be used to infer mobility.

Reliability If applied consistently, the approach to measuring migration using remote sensing technology by averaging physical quantities over pixels can yield reliable migration measures. Algorithms automatically detect changes in visual patterns on satellite or drone images over time. For example, the population size of settlements can be estimated by counting rooftops visible on satellite/drone images. Depending on the proximity and resolution of the image, individuals within certain localities can be identified. Comparing images over time can be used to estimate immigration and emigration into a certain, narrowly defined, location.

Validity The obvious downside of satellite and drone images for measuring migration is that no additional individual-level information about migrants is available: Who is moving, from where, to where, how etc. By itself, remote sensing provides information on how many tents, rooftops or individuals are present in a certain locality, but no information about what happened when there are less dots and shadows the next time new images become available.

Scope There is a rapidly growing number of examples with relevance for migration studies. First, drones and satellite images inform policies and direct aid to refugees. For instance, the United Nations Institute for Training and Research (UNITAR) mapped refugee camps in Jordan and elsewhere with its Operational Satellite Applications Programme. Footnote 11 Civil society organizations such as Human Rights Watch or Amnesty International use satellite imagery to document humanitarian needs of displaced populations at borders or in refugee camps by measuring the growth of settlements. Footnote 12 In this case, satellite images are providing an indication of where aid and assistance are most needed (Bitelli et al., 2017 ; Quinn et al., 2018 ; Shatnawi et al., 2020 ; Tiede et al., 2017 ).

Satellite imagery also forms a key part of the ‘smart border’ agenda, which attempt to use modern technology to improve border management around the world and track ‘illegal’ crossings. Systems relying on remote sensing were developed “to assist border authorities with more effective surveillance and reliable decision-making support” (Al Fayez et al., 2019 ). In contrast, civil society organizations use the same technology to monitor deaths and violations of migrants' rights at the maritime borders of the EU. Footnote 13

For the moment, remote sensing appears to be most useful for informing operations on the ground (managing refugee camps, targeting humanitarian assistance, managing borders etc.) and less for research on migration per se. The technology can also be used to monitor slow onset emigration rates due to changes in climate which can also be inferred from images.

Access With improvements in the quality and accessibility of satellite imagery (Popkin, 2018 ) provided by the European Space Agency, NASA, and others, researchers are also exploring ways to use remote sensing data to measure human migration globally. Public and private bodies offer access to satellite imagery for research purposes and tech companies offer cloud computing power to conduct complex and demanding analyses within minutes. Footnote 14 Depending on the specific data provider, access can be free of charge to research institutes or come with a fee.

Ethics Ethical issues are a key concern for remote censoring technologies because information is collected without the knowledge or consent of individuals. New high-resolution satellite imagery and drone images can identify individuals using face recognition technology. Law enforcement, policing and intelligence agencies use such approaches (Brayne, 2018 ; Hayes, 2017 ; Leese et al., 2021 ; Molnar, 2019 ) which raises serious concerns regarding the situation in undemocratic countries with low data protection standards and policies aiming to suppress and control groups in society. Drones may also be increasingly operated by companies in addition to governments which raises concerns over unknown privacy violations by non-governmental actors.

International air travel

Upon first view, international air passenger traffic belongs to the realm of tourism and transport studies, not migration (see Sect. 2.1.). However, there have been attempts to use this information to infer migration flows. For example. Gabrielli et al. ( 2019 ) used dyadic monthly air passenger traffic between 239 countries and territories worldwide from January 2010 to March 2018 to estimate the number of passengers on commercial flights operated globally. The study explored whether a surplus in travel (increase in travel from A to B but no increase in return travel from B to A within a year) can be linked to migration flows.

Reliability Air passenger data is highly standardized and consistent as it is subject to international industry standards.

Validity Passenger data does not measure migration directly and can only be used to infer different types of migration by inference. Since air passengers data does not allow to track individual passengers or specific cohorts on the basis of their date of entry, researchers need to make assumptions about the length of stay of the passengers. This is problematic because the publicly available data does not indicate who the passengers are, how long they will stay in the country, on which visa they are travelling etc. In addition, flight passenger data is a selective picture of global mobility. 44 percent of registered cross-border travels occur through commercial flights, and that this proportion increases at rising distances between countries (Recchi et al., 2019 ).

Scope Overall, the data may be used to estimate international migration flows if combined with additional data sources. At the moment, the research is still in its exploratory stage and the methods appear underdeveloped. In the future, this approach may bear the potential to measure the level of visa overstayers between countries, one indicator of irregular migration.

Access Air passenger data is collected by flight companies which some make available for purchase. The EU recently made a public and free dataset available. Footnote 15

Ethics Ethical concerns regarding flight data are limited in its current state of the available data. Flight data is aggregated at the country and month level and anonymized. Currently, any misuse for the disadvantage for individuals is unlikely.

Online news data

New advances in technology have made available online news aggregators such as Google News or the Global Database of Events, Language, and Tone (GDELT). Footnote 16 Such platforms monitor the world's news media from nearly every corner of every country in print, broadcast, and web formats. This data has the potential to capture acts of past or prospective migration that were not covered in traditional sources such as administrative data or surveys.

Reliability Migration measures based on online news aggregator data can be considered reliable to the extent that algorithms deriving information on migration apply consistently across all countries and news sources. The issue is that the success of the algorithm in detecting migration may vary by country, by quality of the news outlets, by language and type of migration to be covered. In addition, algorithms may capture the same migration events several times as the same event may have been covered by several news outlets.

Validity The large volume of news articles required to collect information on migration encourages researchers to use language processing algorithms. The emerging evidence is still unclear on how accurately such algorithms may detect events that actually capture migration.

Scope Approaches are still very recent but several uses of this data are available. Carammia et al., ( 2020 ) have used the GDELT database to measure political, social, economic “push factor” events that could motivate people to leave their country. In combination with other data sources, they attempt to forecast displacement and migration with a view to set up early warning systems currently under development in the EU. Footnote 17 In a similar vain, the Internal Displacement Monitoring Centre (IDMC) uses the GDELT database to track internal displacement. Footnote 18 The IOM is also experimenting with such data to improve analysis of the number of migrants that went missing along their journeys, such as the IOM’s missing migrants project (Borja & Black, 2021 ). Apart from eye-witness reports, news articles are the main way to systematically collect data on migrant fatalities and bring light to this tragic topic for policymakers.

Access GDELT and Google News can be accessed online free of charge for researchers.

Ethics Ethical concerns arise in countries with low standards of journalism and data privacy. It is possible, for example, that the identity of individual migrants is revealed in a news article and picked up by automated text analysis. In theory, this information could be used by enforcement agencies to press charges in case of irregular migration or used by smugglers for debt collection. Even when interviewees provide consent for their personal information to be used, they may not be aware that their information may enter migration databases. Such abuses are possible with traditional media sources, however, digital applications may exacerbate the problem by providing cheaper, faster and broader access to data.

Discussion and conclusion

This review highlighted both the enormous opportunity of “big data” and “digital trace data” to complement traditional sources of migration data (see Cesare et al., 2018 ; Hilbert, 2016 ; Hughes et al., 2016 ; Laczko & Rango, 2014 ; Rango & Vespe, 2017 ; Sîrbu et al., 2021 ) and the main challenges and risks associated with such data. Several broader conclusions can be drawn from the above discussion on the eight discussed sources (see Table 1 for a summary):

The main advantages of digital data sources for migration scholars are captured by the first two V’s of the “3 V’s definition” of big data introduced in Sect.  3.2 : Volume and velocity. In some cases, digital data sources provide information of millions of individuals in almost real-time. This provides migration researchers with the possibility explore migration trends where administrative data sources, surveys and censuses (sources traditionally used for inferring migration) are not available (such as in many low-income contexts), not accessible or too slow (for example in contexts of displacement and forced migration that are unfolding rapidly). Another key advantage is its granularity by providing “high-resolution” information. Digital data sources, especially approaches leveraging remote sensing technologies or mobile cell phones, often allow researchers to zoom into migration events at the sub-national, sub-regional or even local level. Nationally representative survey data, for example, often lacks sufficient sample size to disaggregate to the level of regions, districts or cities.

Unlike “traditional” sources, new data sources often make no distinction in terms of the “legal residence status” of individuals. Anyone using a digital service in included in the data. As a result, the volume, granularity and status-agnostics of many digital data sources offer new opportunities to collect information on “hard-to-reach” populations such as recent migrants, displaced or forced migrants and irregular migrants which are often excluded from ‘official’ data sources such as population registers or surveys (Cesare et al., 2018 ; Massey & Capoferro 2004 ; Reichel & Morales, 2017 ). Lastly, a key advantage to migration scholars is the fact that many data sources are accessible online and free of charge.

The review has also highlighted major challenges associated with using digital data sources for inferring migration. ‘Digital trace’ data is largely collected by private companies who offer services to their users and use user data to target advertisements or sell data to third parties. These data are not designed for research purposes. This has important implications both on ethical (Beduschi, 2020 , Brayne, 2018 ; Cesare et al., 2018 ; Hayes, 2017 , Latonero & Kift, 2018 ; Leese et al., 2021 ; Molnar, 2019 ; Sîrbu et al., 2020 ; Zwitter, 2014 ) and empirical grounds in terms of reliability and validity of migration measurement (Cesare et al., 2018 , Ruel et al., 2016 ; Sîrbu et al., 2020 ).

First, there are severe ethical concerns regarding the use of digital data sources including the limited awareness of users regarding the extent of and purposes for which their data is being used and the risk of harm for individual migrants in cases where information is used by law enforcement, border management, intelligence agencies or smugglers (Brayne, 2018 ; Hayes, 2017 ; Molnar, 2019 ). The first rule that a researcher must follow is to acknowledge that data are people and can do harm (Sîrbu et al., 2021 ). Data may include information on particular vulnerable groups such as refugees, irregular migrants, persons displaced by disasters. Some may be persecuted by authorities in origin and destination countries. Researchers must ensure ethical standards for data use that protect vulnerable groups from identification and possible discrimination (Cesare et al., 2018 ).

Violations of data privacy and protection standards are especially concerning in undemocratic countries with low data protection standards, limited rule-of-law, and a lack of democratic norms. In extreme cases, new technologies can enable “digital authoritarianism” and “Orwellian state surveillance” (Dragu & Lupu, 2020 ). Three examples illustrate the extent of real risks: China’s social credit system, for example, leverages smartphone location data, social media communication, travel records, purchase records, camera data and facial recognition, among others, in combination with various administrative records to assign a social credit to its citizen. Low scores could be used to prevent access to a passport or visa needed to leave the country. Footnote 19 After departure of US troops, the Taliban have reportedly considered using US-made digital identity technology to persecute Afghans who have worked with the international coalition. Funded by millions of donor funding, Afghanistan’s National Statistics and Information Authority launched a digital biometric identity card including fingerprints, iris scans and a photograph, as well as voter registration databases. Footnote 20 In 2018, Bangladesh shared hundreds of thousands of data of Rohingya refugees collected by UNHCR with Myanmar then used to facilitate potential repatriation. Footnote 21

Unlike states, researchers often do not have access to individual-level information from digital sources, however, they must be aware of the potential harms for individuals and groups when using digital data sources and must review the data providers’ data protection and privacy standards. Researchers are advised to seek ethical approval by a scientific committee when dealing with digital data and migration.

Apart from ethics, the review has highlighted many empirical challenges. Reliability and validity of digital data sources for inferring migration must be considered when engaging in research. It is often not transparent how exactly key measures of migration are generated (i.e. Facebook, Google). There are also concerns regarding “generalizability” of digital data as the user base of various digital services is often selective and does not represent the general population at large (Cesare et al., 2018 ; Sîrbu et al., 2020 ). Digital data is often made available at highly aggregated levels. This severely limits the analytical potential for migration scholars who are often interested in measuring migration at the individual (micro) level. Moreover, digital data often remains “thin” offering very few additional information beyond time and location such as socio-demographic or socio-economic characteristics of migration, the reasons and channels of migration or the expected duration of stay. This further limits its analytical use especially if the data is not combined with other data sources. Traditional surveys usually do not face these issues (but many others) as they are tailored for answering specific research questions.

Lastly, many populations are excluded from a variety of digital data sources despite technological advances worldwide. For those data relying in digital traces such as social media or online searches, it is still a long way to obtain a comprehensive picture of global mobility as smartphone user penetration reached 38.5 percent in 2020 and half the world population is still offline today. Footnote 22

Looking ahead, several trends are already unfolding. First, new breakthroughs in measuring migration research will stem from a combination of different sources (e.g. Alexander et al., 2020 ; Sîrbu et al., 2020 ; Snijders et al., 2012 ). Given the ‘representativeness’ issue of digital trace data, traditional data is needed for “ground truthing” (i.e. cross-validating data by comparing it with other ‘official’ data sources). To address, the “thinness” of digital data, combining data provides large opportunities to add richness to the analysis. One example is using social media, online search, or mobile phone data to locate migration events or patterns and then target surveys in certain geographies or adjust administrative data collection accordingly (Alexander et al., 2020 ).

The second trend is further convergence and integration of academic disciplines around the issue of measuring migration (e.g. Miller et al., 2019 ). Different disciplines such as earth sciences, climate research, security studies, tourism and transport studies, computer science, sociology, economics, demography, ethnography, library sciences and political science bring different tools, methodologies and technologies to the table which will likely see the field become even more interdisciplinary. As a result, more interdisciplinary dialogue is needed to advance the field.

As the field is changing at a dizzying speed, this paper attempted to provide a brief overview and reflection on the main new digital data sources. The aim of this review was to provide incoming migration researchers with a menu of options and seasoned researchers with an update on new approaches. The information provided assists researchers in making difficult trade-offs when approaching their research question and policy analysts with a broad understanding of the limitations of the data they use.

The review has two obvious limitations. First, given the complex and rapidly growing field it seems near impossible to cover every existing approach and to cover the literature in all its breath. The review is focused on the main approaches without any claim to be exhaustive. Second, the field is rapidly evolving. This means that new research will have become available already by the time of publication.

The toolbox for migration researchers will become bigger, more diverse, but also more powerful due to new opportunities of digital data. Despite the ‘gold rush’ on big and digital data, the review also cautioned migration scholars in view of the many ethical and empirical obstacles for inferring migration based on digital data sources. The review aimed to contribute to a balanced understanding of these new data sources to facilitate knowledge accumulation and interdisciplinary dialogue in the field of migration studies.

Availability of data and materials

Not applicable.

Change history

13 may 2022.

In the online version of this article, there was a typo in the funding note. The article has been updated.

The GCM is the first comprehensive, inter-governmentally negotiated (non-binding) treaty on migration adopted in 2018 by 152 countries, highlights the importance of data and evidence throughout its 23 objectives. The first goal of the GCM itself is improving migration data across the board. The SDGs are the follow-up to the UN Millennium Goals and feature several migration-relevant goals and include indicators to measure progress towards them. New approaches to measuring migration based on “innovative” data sources have mainly been pioneered by academic scholars, yet some of this work has long caught the attention of key national and international governmental stakeholders. In 2009, the United Nations Global Pulse initiative was launched to use new data sources for analysis of development projects and processes, including migration issues. In 2018, the European Commission, in partnership with the IOM Global Migration Data Analysis Centre, launched the ‘Big Data for Migration Alliance’ with the aim of sharing knowledge on data innovation in the field of migration, providing technical support to local and national administrations interested in using new data sources, and testing new data applications for specific policy needs.

There are exceptions. The collection, harmonisation and estimation of migration data within the EU (Poulain et al., 2006 ; Raymer et al., 2013 ) and compilation of data on migration flows in Latin America (Lemaitre, 2005 ) are key achievements. Data on migration in many non-OECD countries remains limited.

Mobility (migration regardless of distance and borders) more broadly has traditionally been the focus of transport studies and urban planning (e.g. Pappalardo et al., 2015 ; Song et al., 2010 ).

There has been some indication that intentions (also expressed in Google searches) are in fact a relevant predictor of future migration both at the national and international levels (e.g. Van Dalen & Henkens, 2013 ; Tjaden et al., 2019 ; Böhme et al., 2018 ).

Censuses are population counts and are used to calculate ‘stocks’ of migrants (Bilsborrow et al., 1997 ; Global Migration Group, 2017 ; White, 2016 ). Administrative data are collected by governments for the purpose of providing certain services or enforcing certain laws and, thus, may include records of migrants subject to a particular law or service. They may include population registers; visas; immigration, expatriation and asylum records; border entries; work permit registers; tax records, and health insurance or social insurance records (Bilsborrow, 2016 ; Global Migration Group, 2017 ; Lemaitre, 2005 ; Poulain et al., 2006 ; Willekens et al., 2017 ). Sample surveys are a common approach to measuring migration, especially in research, given its’ flexible choice of location, target group and thematic scope (Bilsborrow, 2016 ; Bilsborrow et al., 1997 ; Fawcett & Arnold, 1987 ; Goldstein & Goldstein, 1981 ).

Extended Detail Records (XDRs) and Control Plane Records (CPRs) also record locations when something is downloaded or phones are switching antennas providing more complete coverage.

Measuring human mobility (within countries, regions or cities) is an exploding field of research spanning physics and network science, to data mining, and has fueled advances from public health to transportation engineering, urban planning, official statistics and the design of smart cities (see e.g. Song et al., 2010 ; Pappalardo et al., 2015 ).

Researchers are working to address the methodological challenges associated with such (‘self-selection’) bias, and results look promising (Spyratos et al., 2019 ; Zagheni et al., 2017 ; Hughes et al., 2016 ).

Europol, Fontex and EASO as well as EU member states have been actively been monitoring communication in Facebook groups relevant for organizing migration, for example, from the Middle East and Africa to the EU. Information on prices of forged documents or sea transform offered by smugglers provide indication on changes in the volume and direction of migration flows. EASO was stopped collecting the data by the EU’s own data protection watchdog, see https://euobserver.com/investigations/146856 . In theory, it is possible to collect information on users’ profiles and monitor where those users report their location online a year later. This controversial approach has been tried successfully, yet no public evidence has been released.

https://euobserver.com/investigations/146856

https://unitar.org/sustainable-development-goals/satellite-analysis-and-applied-research

https://earthi.space/blog/satellite-solution-refugee-crisis/

https://www.hrw.org/news/2016/09/07/jordan-new-satellite-images-syrians-stranded-border

http://www.satsentinel.org/

https://www.unglobalpulse.org/2020/02/pulsesatellite-a-collaboration-tool-using-human-ai-interaction-to-analyse-satellite-imagery/

For example, governments use drone imagery to monitor immigration attempts in the Mediterranean Sea and at Europe’s land borders (Bhadwal et al., 2019 ; Dijstelbloem, 2017 ) or to monitor border crossing attempts at the Mexican-US border (see https://www.gao.gov/assets/690/682842.pdf ). Greek and EU authorities use satellite imagery to monitor crossing attempts (ibid.). NGOs and universities also use the same information to document human rights abuses by, for example, using satellite imagery and other evidence to reconstruct the journey of a boat with migrants that lost dozens passengers upon its return to Tripoli (Dijstelbloem, 2017 ). Although the boat had been spotted by several aircraft and vessels, no rescue operation had been mounted.

See for example https://earth.esa.int/eogateway/ ; https://search.earthdata.nasa.gov/search ; https://earthexplorer.usgs.gov/

See the EU Knowledge Centre for Migration and Demography’s Dynamic Data Hub, at:  https://bluehub.jrc.ec.europa.eu/migration/app/?state=5d6005b30045242cabd750a2 .

GDELT is a repository of 316 types of geolocated event reported in the world’s broadcast, print and web media, in 100 languages.

Frontex, EASO and JRC are all developing early warning, forecasting and foresight approaches.

https://www.internal-displacement.org/expert-opinion/idetect-how-technology-and-collaboration-between-innovators-can-help-ensure-no-one

The system has reportedly been used to suppress and control the Uighur minority in China’s Xinjiang region. Analysis to linked data from various digital data sources alerts enforcement agencies at checkpoints when Uighurs approach the limits of their neighbourhood. (see Ross Andersen in the Atlantic: “The panopticon is already here”, available at https://www.theatlantic.com/magazine/archive/2020/09/china-ai-surveillance/614197/

See Emrys Schoemaker, 7 September 2021 in the Guardian: “The Taliban are showing us the dangers of personal data falling into the wrong hands “, available at https://www.theguardian.com/global-development/2021/sep/07/the-taliban-are-showing-us-the-dangers-of-personal-data-falling-into-the-wrong-hands

See Human Rights Watch on 21 June 2021: “UN Shared Rohingya Data Without Informed Consent”, available from https://www.hrw.org/news/2021/06/15/un-shared-rohingya-data-without-informed-consent

https://data.worldbank.org/indicator/IT.NET.USER.ZS

Al Fayez, F., Hammoudeh, M., Adebisi, B., & Abdul Sattar, K. N. (2019). Assessing the effectiveness of flying ad hoc networks for international border surveillance,  International Journal of Distributed Sensor Networks ,  15 (7), 1–12.

Alexander, M., Polimis, K., & Zagheni, E. (2020). Combining social media and survey data to Nowcast migrant stocks in the United States. arXiv preprint https://arxiv.org/abs/2003.02895 .

Beduschi, A. (2020). International migration management in the age of artificial intelligence.  Migration Studies . https://doi.org/10.1093/migration/mnaa003 .

Bengtsson, L., Lu, X., Thorson, A., Garfield, R., & Von Schreeb, J. (2011). Improved response to disasters and outbreaks by tracking population movements with mobile phone network data: a post-earthquake geospatial study in Haiti. PLoS Medicine, 8 (8), e1001083.

Bhadwal, N., Madaan, V., Agrawal, P., Shukla, A., & Kakran, A. (2019). Smart border surveillance system using wireless sensor network and computer vision. In 2019 international conference on Automation, Computational and Technology Management (ICACTM) (pp. 183–190). London. https://doi.org/10.1109/ICACTM.2019.8776749 .

Bilsborrow, R. E. (2016). Concepts, definitions and data collection approaches. In M. J. White (Ed.), International handbook of migration and population distribution (pp. 109–156). Springer.

Google Scholar  

Bilsborrow, R. E., Hugo, G., & Oberai, A. S. (1997). International migration statistics: Guidelines for improving data collection systems . International Labour Organization.

Bitelli, G., Eleias, M., Franci, F., & Mandanici, E. (2017). VHR satellite imagery for humanitarian crisis management: A case study. In:  Fifth international conference on remote sensing and geoinformation of the environment (RSCy2017) , 10444, p. 104440T. International Society for Optics and Photonics.

Böhme, J., Gröger, A., & Stöhr, T. (2018). Searching for a better life: Predicting international migration with online search keywords. Journal of Development Economics,   142, 1–14.

Borja, A. G., & Black, J. (2021). Measuring migrant deaths and disappearances. Forced Migration Review, 66 , 58–60.

Brayne, S. (2018). The criminal law and law enforcement implications of big data. Annual Review of Law and Social Science, 14 , 293–308.

Article   Google Scholar  

Brenner, Y., & Frouws, B. (2019). Hype or hope? Evidence on use of smartphones & social media in mixed migration. Mixed Migration Centre, Geneva.

Carammia, M., Iacus, S. M., & Wilkin, T. (2020). Forecasting asylum-related migration flows with machine learning and data at scale. arXiv preprint arXiv:2011.04348 .

Cesare, N., Lee, H., McCormick, T., Spiro, E., & Zagheni, E. (2018). Promises and pitfalls of using digital traces for demographic research. Demography, 55 (5), 1979–1999.

Chi, G., Lin, F., Chi, G., & Blumenstock, J. (2020). A general approach to detecting migration events in digital trace data`. PLoS ONE, 15 (10), e0239408.

Clemens, M., Summers, L. H., & Santo Tomas, P. A. (2009). Migrants count: Five steps towards better migration data. In Report of the commission on international migration data for development research and policy. Center for Global Development.

Czaika, M., & Orazbayev, S. (2018). The globalisation of scientific mobility, 1970–2014. Applied Geography, 96 , 1–10.

Dekker, R., Engbersen, G., Klaver, J., & Vonk, H. (2018). Smart refugees: How Syrian asylum migrants use social media information in migration decision-making.  Social Media+ Society ,  4 (1), 2056305118764439.

Dijstelbloem, H. (2017). Migration tracking is a mess. Nature, 543 (7643), 32–34.

Dragu, T., & Lupu, Y. (2021). Digital authoritarianism and the future of human rights.  International Organization , 75 (4), 991–1017.

Fawcett, J. T., & Arnold, F. (1987). The role of surveys in the study of international migration: An appraisal. International Migration Review, 21 (4), 1523–1540.

Fiori, L., Abel, G., Cai, J., Zagheni, E., Weber, I., & Vinué, G. (2017). Using Twitter data to estimate the relationship between short-term mobility and long-term migration. In Proceedings of the 2017 ACM on web science conference (pp. 103–110).

Gabrielli, L., Deutschmann, E., Natale, F., Recchi, E., & Vespe, M. (2019). Dissecting global air traffic data to discern different types and trends of transnational human mobility. EPJ Data Science, 8 (1), 26.

Gandomi, A., & Haider, M. (2015). Beyond the hype: Big data concepts, methods, and analytics. International Journal of Information Management, 35 (2), 137–144.

Global Migration Group. (2017). Handbook for improving the production and use of migration data for development. In Global Knowledge Partnership for Migration and Development (KNOMAD) . World Bank.

Goldstein, S., & Goldstein, A. (1981). Surveys of migration in developing countries: A methodological review. Papers of the East-West Population Institute, 71 , 120.

Hayes, B. (2017). Migration and data protection: Doing no harm in an age of mass displacement, mass surveillance and “big data”. International Review of the Red Cross , 99 (904), 1Ý79–209.

Hilbert, M. (2016). Big data for development: A review of promises and challenges. Development Policy Review, 34 (1), 135–174.

Hughes, C., Zagheni, E., Abel, G. J., Sorichetta, A., Wi’sniowski, A., Weber, I., & Tatem, A. J. (2016). Inferring migrations: Traditional methods and new approaches based on mobile phone, social media, and other big data: Feasibility study on inferring (labour) mobility and migration in the European Union from Big Data and Social Media Data . European Commission.

IOM (2020). ‘Chapter 3: Migration Research and Analysis: Growth, Reach and Recent Contributions’. In: World Migration Report 2020 . Geneva.

Kikas, R., Dumas, M., & Saabas, A. (2015). Explaining international migration in the skype network: The role of social network features. In: Proceedings of the 1st ACM Workshop on Social Media World Sensors (pp. 17–22).

Kraemer, M. U., Sadilek, A., Zhang, Q., Marchal, N. A., Tuli, G., Cohn, E. L., Hswen, Y., Perkins, T. A., Smith, D. L., Reiner Jr. R. C., & Brownstein, J. S. (2020). Mapping global variation in human mobility. Nature Human Behaviour, 4 (8), 800–810.

Laczko, F. (2016). Improving Data on International Migration and Development: Towards a Global Action Plan?’ Conference Paper, Improving Data on International Migration – Towards Agenda 2030 and the Global Compact on Migration , 1–3 December, 2016, German Federal Foreign Office.

Laczko, F., & Rango, M. (2014). Can big data help us achieve a “Migration Data Revolution”? Migration Policy Practice (IOM), 4 (2), 20–29.

Latonero, M., & Kift, P. (2018). On digital passages and borders: Refugees and the new infrastructure for movement and control.  Social Media+ Society ,  4 (1), 1–11.

Laudel, G. (2003). Studying the brain drain: Can bibliometric methods help? Scientometrics, 57 (2), 215–237.

Leese, M., Noori, S., & Stephan S. (2021). Data matters: The politics and practices of digital border and migration management.  Geopolitics . https://doi.org/10.1080/14650045.2021.1940538 .

Lemaitre, G. (2005). The comparability of international migration statistics: Problems and prospects. Statistics Brief, 9 , 1–8.

Lin, A. Y., Cranshaw, J., & Counts, S. (2019). Forecasting US domestic migration using internet search queries. In: The world wide web conference (pp. 1061–1072).

Martín, Y., Cutter, S. L., Li, Z., Emrich, C. T., & Mitchell, J. T. (2020). Using geotagged tweets to track population movements to and from Puerto Rico after hurricane Maria. Population and Environment, 1 (1), 1–24.

Massey, D., & Capoferro, C. (2004). Measuring undocumented migration. The International Migration Review, 38 (3), 1075–1102.

Miller, H. J., Dodge, S., Miller, J., & Bohrer, G. (2019). Towards an integrated science of movement: Converging research on animal movement ecology and human mobility science. International Journal of Geographical Information Science, 33 (5), 855–876.

Moed, H. F., & Halevi, G. (2014). A bibliometric approach to tracking international scientific migration. Scientometrics, 101 (3), 1987–2001.

Molnar, P. (2019). Technology on the margins: AI and global migration management from a human rights perspective. Cambridge International Law Journal, 8 (2), 305–330.

Pappalardo, L., Simini, F., Rinzivillo, S., Pedreschi, D., Giannotti, F., & Barabási, A. L. (2015). Returners and explorers dichotomy in human mobility. Nature Communications, 6 (1), 1–8.

Pisarevskaya, A., Levy, N., Scholten, P., & Jansen, J. (2019). Mapping migration studies: An empirical analysis of the coming of age of a research field. Migration Studies, 8 (3), 455–481.

Popkin, G. (2018). Technology and satellite companies open up a world of data. Nature, 557 (7706), 745–748.

Poulain, M., Perrin, N., & Singleton, A. (2006). Towards harmonised european statistics on international migration . Presses Universitaires de Louvain.

Quinn, J. A., Nyhan, M. M., Navarro, C., Coluccia, D., Bromley, L., & Luengo-Oroz, M. (2018). Humanitarian applications of machine learning with remote-sensing data: Review and case study in refugee settlement mapping. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences ,  376 (2128). 1–16.

Rango, M., & Vespe, M. (2017). Big data and alternative data sources on migration: from case-studies to policy support. Summary Report. Ispra: European Commission Joint Research Centre.

Raymer, J., Wiśniowski, A., Forster, J. J., Smith, P. W., & Bijak, J. (2013). Integrated modeling of European migration. Journal of the American Statistical Association, 108 (503), 801–819.

Recchi, E., Deutschmann, E., & Vespe, M. (2019). Estimating transnational human mobility on a global scale. Robert Schuman Centre for Advanced Studies Research Paper No. RSCAS, 30.

Reichel, D., & Morales, L. (2017). Surveying immigrants without sampling frames—Evaluating the success of alternative field methods. ComparatIve Migration Studies, 5 (1), 1.

Ruel, E., Wagner III, W., & Gillespie, B. (2016). The quality of measurement: reliability and validity. The practice of survey research: Theory and applications.

Ruktanonchai, N. W., Ruktanonchai, C. W., Floyd, J. R., & Tatem, A. J. (2018). Using Google Location History data to quantify fine-scale human mobility. International Journal of Health Geographics, 17 (1), 1–13.

Sanchez, G., Hoxhaj, R., Nardin, S., Geddes, A., Achilli, L., & Kalantaryan, S. (2018). A study of the communication channels used by migrants and asylum seekers in Italy, with a particular focus on online and social media.

Shatnawi, N., Weidner, U., & Hinz, S. (2020). Monitoring urban expansion as a result of refugee fluxes in North Jordan using remote sensing techniques. Journal of Urban Planning and Development,  146 (3), 1–32.

Sîrbu, A., Andrienko, G., Andrienko, N., Boldrini, C., Conti, M., Giannotti, F., & Pappalardo, L. (2020). Human migration: the big data perspective.  International Journal of Data Science and Analytics, 11 (0), 1–20. https://doi.org/10.1007/s41060-020-00213-5 .

Snijders, C., Matzat, U., & Reips, U. D. (2012). Big data: Big gaps of knowledge in the field of internet science. International Journal of Internet Science, 7 (1), 1–5.

Song, C., Qu, Z., Blumm, N., & Barabási, A. L. (2010). Limits of predictability in human mobility. Science, 327 (5968), 1018–1021.

Spyratos, S., Vespe, M., Natale, F., Weber, I., Zagheni, E., & Rango, M. (2019) ‘Quantifying International Human Mobility Patterns Using Facebook Network Data. PLoS ONE ,  14 (10), 1–22.

State, B., Rodriguez, M., Helbing, D., & Zagheni, E. (2014). Migration of professionals to the U.S.: Evidence from linkedin data. In L. M. Aiello, & D. McFarland (Eds.), 6th international conference on social informatics , SocInfo (pp. 531–543). Springer.

Sudakova, A. E., & Tarasyev, A. A. (2019). Digitalization and scientometrics in assessing the migration of scientists. In  International scientific and practical conference on digital economy (ISCDE 2019). Atlantis Press.

Tiede, D., Krafft, P., Füreder, P., & Lang, S. (2017). Stratified template matching to support refugee camp analysis in OBIA workflows. Remote Sensing, 9 (4), 326.

Tjaden, J., Arau, A., Nuermaimaiti, M., Cetin, I., Acostamadiedo, E., & M. Rango (2021). Using “Big Data” to forecast migration—A tale of high expectations, promising results and a long road ahead’. MEDIUM. Available at https://medium.com/@UNmigration/using-big-data-to-forecast-migration-8c8e64703559 .

Tjaden, J., Auer, D., & Laczko, F. (2019). Linking migration intentions with flows: Evidence and potential use. International Migration, 57 , 36–57.

UN DESA. (2017). ‘UN Handbook on Measuring International Migration through Population Censuses’. In: Economic and Social Affairs . New York.

UN DESA. (2019). International Migration 2019. Department of Economic and Social Affairs, Population Division, New York City.

UN Global Pulse. (2014). Estimating Migration Flows Using Online Search Data. Global Pulse Project Series , 4 , 1–2.

UN Global Pulse. (2017) Social media and forced displacement: Big data analytics & machine-learning , Geneva.

UNHCR. (2020). UNHCR Global Trends - Forced displacement in 2020. United Nations High Commissioner for Refugees, Geneva.

Van Dalen, H. P., & Henkens, K. (2013). Explaining emigration intentions and behaviour in the Netherlands, 2005–2010. Population Studies, 67 (2), 225–241.

Wang, Y., Luo, H., & Shi, Y. (2019). Complex network analysis for international talent mobility based on bibliometrics. International Journal of Innovation Science, 11 (3), 419–435.

White, M. J. (Ed.). (2016). International Handbook of Migration and Population Distribution (vol. 6) . Springer.

Willekens, F., Massey, D., & Raymer, J. (2017). International migration under the microscope. Science, 352 (6288), 897–899.

Williams, N. E., Thomas, T. A., Dunbar, M., Eagle, N., & Dobra, A. (2015). Measures of human mobility using mobile phone records enhanced with GIS Data. PLoS ONE, 10 (7), 1–16.

Zagheni, E., Garimella, V. R. K., Ingmar, W., & State, B. (2014). Inferring international and internal migration patterns from twitter data. In Proceedings of the 23rd International Conference on World Wide Web (pp. 439–44). ACM Press.

Zagheni, E., & Weber, I. (2012). You are where you e-mail: Using e-mail data to estimate international migration rates. In Proceedings of the 4th annual ACM web science conference (pp. 348–351). ACM Press.

Zagheni, E., Weber, I., & Gummadi, K. (2017). Leveraging Facebook’s advertising platform to monitor stocks of migrants. Population and Development Review, 43 , 721–734.

Zwitter, A. (2014). Big data ethics. Big Data and Society, 1 (2), 2053951714559253.

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Acknowledgements

The author would like to thank Marzia Rango (IOM), Emilio Zagheni (Max Planck Institute for Demographic Research), Ingmar Weber (Qatar Computing Research Institute) and Teddy Wilkin (EASO) for numerous discussions and presentations on the potential of digital trace data for measuring migration which motivated the idea for this paper.

Open Access funding enabled and organized by Projekt DEAL.

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Immigration fuels the American economy, feeds the talent pool, and can directly affect company performance. And yet few executives and entrepreneurs have waded into the policy dialogue, says James Heskett. Open for comment; 0 Comments.

• 30 Mar 2021
• Working Paper Summaries

Whose Job Is It Anyway? Co-Ethnic Hiring in New US Ventures

The impact of immigration has been particularly sharp in entrepreneurship, yet there is remarkably little evidence about how immigration in the workplace connects to the creation and scaling of new firms. The economic consequences of greater workplace and entrepreneurial diversity deserve closer attention.

• 11 Jan 2021

The Political Effects of Immigration: Culture or Economics?

This paper reviews and explains the growing literature focused on the political effects of immigration, and highlights fruitful avenues for future research. When compared to potential labor market competition and other economic forces, broadly defined cultural factors have a stronger political and social impact.

• 03 Nov 2020

An Executive Order Worth $100 Billion: The Impact of an Immigration Ban’s Announcement on Fortune 500 Firms’ Valuation

President Trump’s executive order restricting entry of temporary foreign workers to the United States negatively affected the valuation of 471 publicly traded Fortune 500 firms by an estimated $100 billion. Closed for comment; 0 Comments.

• 15 Jun 2020

The Seeds of Ideology: Historical Immigration and Political Preferences in the United States

Researchers test the relationship between historical immigration to the United States and political ideology today.

• 11 May 2020

Immigration Policies Threaten American Competitiveness

At this time of crisis, America risks signaling to global innovators and entrepreneurs that they have no future here, says William R. Kerr. Open for comment; 0 Comments.

• 21 Apr 2020

Changing In-group Boundaries: The Role of New Immigrant Waves in the US

How do new immigrants affect natives’ views of other minority groups? This work studies the evolution of group boundaries in the United States and indicates that whites living in states receiving more Mexican immigrants recategorize blacks as in-group members, because of the inflow of a new, “affectively” more distant group.

• 06 Apr 2020

Where Do Workers Go When the Robots Arrive?

Marco Tabellini and colleagues investigate where workers go after losing their jobs to automation and Chinese imports. Open for comment; 0 Comments.

• 17 Feb 2020

The Impact of Technology and Trade on Migration: Evidence from the US

Labor mobility can re-equilibrate local labor markets after an economic shock. Both robot adoption and Chinese import competition between 1990 and 2015 caused large declines in manufacturing employment across US local labor markets (commuting zones, CZs). However, only robots were associated with a decline in CZ population, which resulted from reduced in-migration rather than by increased out-migration.

• 01 Jan 2020

Why Not Open America's Doors to All the World’s Talent?

SUMMING UP: The H-1B visa program is exploited by some employers to replace high-paid talent, but that doesn't mean foreign workers should be shut out of working in the United States, according to many of James Heskett's readers. Open for comment; 0 Comments.

• 19 Jun 2019

Migrant Inventors and the Technological Advantage of Nations

This study provides robust econometric evidence for how immigrant inventors shape the innovation dynamics of their receiving countries. Countries receiving inventors from other nations that specialize in patenting particular technologies are more likely to have a significant increase in patent applications of the same technology.

• 08 Jun 2019

The Gift of Global Talent: Innovation Policy and the Economy

High-skilled workers in today’s knowledge-based economy are arguably the most important resource to the success of businesses, regions, and industries. This chapter pulls from Kerr’s book The Gift of Global Talent to examine the migration dynamics of high-skilled individuals. He argues that improving our knowledge of high-skilled migration can lead to better policy decisions.

• 07 Feb 2019

Immigrant Networking and Collaboration: Survey Evidence from CIC

This study compares United States-born and immigrant entrepreneurs’ use of networking opportunities provided by CIC, the former Cambridge Innovation Center. Immigrants clearly take more advantage of networking opportunities at CIC, especially around the exchange of advice. It remains to be seen whether this generates long-term performance advantages for immigrants.

• 01 Nov 2018

Forecasting Airport Transfer Passenger Flow Using Real-Time Data and Machine Learning

Passengers arriving at international hubs often endure delays, especially at immigration and security. This study of London’s Heathrow Airport develops a system to provide real-time information about transfer passengers’ journeys through the airport to better serve passengers, airlines, and their employees. It shows how advanced machine learning could be accessible to managers.

• 01 Oct 2018

Is the US Losing its Ability to Attract Highly Skilled Migrant Workers?

As debates sharpen on the benefits and drawbacks of migrant labor, William R. Kerr's new book explores why global talent flows matter to national economic development and security. Book excerpt and author interview. Open for comment; 0 Comments.

• 19 Sep 2018

From Immigrants to Americans: Race and Assimilation During the Great Migration

The Great Migration of African Americans and the mass migration of Europeans both contributed to forming the modern American racial and ethnic landscape. This analysis finds that native whites more readily accepted European immigrants as African Americans arrived in the US North during the first Great Migration, facilitating the assimilation of European immigrants in northern urban centers.

• 07 Aug 2018

Gifts of the Immigrants, Woes of the Natives: Lessons from the Age of Mass Migration

Investigating the economic and political effects of immigration across US cities between 1910 and 1930, this paper finds that political opposition to immigration can arise even when immigrants bring widespread economic benefits. The paper provides evidence that cultural differences between immigrants and natives were responsible, at least in part, for natives’ anti-immigration reactions.

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State of the Union 2024: Where Americans stand on the economy, immigration and other key issues

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The U.S. Border Patrol had nearly 250,000 encounters with migrants crossing into the United States from Mexico in December 2023.

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About migration

World Migration Report 2024 Reveals Latest Global Trends and Challenges in Human Mobility 

• International remittances surged by 650 per cent, from USD 128 billion to USD 831 billion between 2000 and 2022. 
• Migrant remittances surpass foreign direct investment in boosting the GDP of developing nations. 
• 281 million international migrants globally; number of those displaced hit a record high by the end of 2022 at 117 million.  

To access the World Migration Report 2024, visit the WMR website . 

Dhaka/Geneva, 7 May – The International Organization for Migration (IOM) today launched the World Migration Report 2024 , which reveals significant shifts in global migration patterns, including a record number of displaced people and a major increase in international remittances.  

IOM Director General Amy Pope formally released the report in Bangladesh, which stands at the forefront of migration challenges, including emigration, immigration and displacement.   

“The World Migration Report 2024 helps demystify the complexity of human mobility through evidence-based data and analysis,” IOM Director General Amy Pope said at the launch. “In a world grappling with uncertainty, understanding migration dynamics is essential for informed decision-making and effective policy responses, and the World Migration Report advances this understanding by shedding light on longstanding trends and emerging challenges.” 

The report highlights that international migration remains a driver of human development and economic growth, highlighted by a more than 650 per cent increase in international remittances from 2000 to 2022, rising from USD 128 billion to USD 831 billion. The growth continued despite predictions from many analysts that remittances would decrease substantially because of COVID-19.  

Of that 831 billion in remittances, 647 billion were sent by migrants to low– and middle-income countries. These remittances can constitute a significant portion of those countries' GDPs, and globally, these remittances now surpass foreign direct investment in those countries. 

Highlighting key findings, the report reveals that while international migration continues to drive human development, challenges persist. With an estimated 281 million international migrants worldwide, the number of displaced individuals due to conflict, violence, disaster, and other reasons has surged to the highest levels in modern-day records, reaching 117 million, underscoring the urgency of addressing displacement crises.  

Migration, an intrinsic part of human history, is often overshadowed by sensationalized narratives. However, the reality is far more nuanced than what captures headlines. Most migration is regular, safe, and regionally focused, directly linked to opportunities and livelihoods. Yet, misinformation and politicization have clouded public discourse, necessitating a clear and accurate portrayal of migration dynamics.  

By choosing Dhaka as the report's launch site, IOM not only highlights the country's efforts in supporting vulnerable migrants and fostering pathways for regular migration but also recognizes Bangladesh's important role in shaping global migration discourse and policy.  

As a Global Compact for Safe, Orderly, and Regular Migration Champion country, Bangladesh has demonstrated a strong commitment to addressing migration issues and implementing policies that safeguard migrants' rights. This proactive engagement aligns with IOM's strategic objectives, making Bangladesh an ideal location to launch the 2024 World Migration Report.  

IOM’s World Migration Report, with its innovative digital tools and comprehensive analysis, aims to help dispel myths, provide critical insights, and inspire meaningful action in addressing the challenges and opportunities of human mobility.  

“We hope the report inspires collaborative efforts to harness the potential of migration as a driver for human development and global prosperity,” DG Pope said. 

“As one of the GCM champion countries, Bangladesh will not only continue to act upon the pledges it has made for its domestic context but would also take up emerging issues and challenges pertaining to migration and development for informed deliberations at the international level,” said Dr. Hasan Mahmud, Honourable Foreign Minister, Government of the People’s Republic of Bangladesh.

Notes to editors: 

This launch is part of IOM Director General’s first three-day visit to Bangladesh. 

For more information, please contact: 

Marie McAuliffe, World Migration Report Editor at [email protected]  

For media requests: Florence Kim at [email protected]  

RELATED NEWS

Joint statement by japan, norway, sweden, switzerland and the united states following their visit to the rohingya refugee camps in cox’s bazar, bangladesh, 75.9 million people living in internal displacement in 2023: idmc report, iom chief visits bangladesh, secures funding commitments for rohingya refugees, floods displace thousands in east africa; iom calls for sustained efforts to address climate mobility.

Migration updates 

Subscribe to IOM newsletter to receive the latest news and stories about migration.

• Media Resources
• 2030 Agenda

World Migration Report 2024 Reveals Latest Global Trends and Challenges in Human Mobility 

• International remittances surged by 650 per cent, from USD 128 billion to USD 831 billion between 2000 and 2022. 
• Migrant remittances surpass foreign direct investment in boosting the GDP of developing nations. 
• 281 million international migrants globally; number of those displaced hit a record high by the end of 2022 at 117 million.  

Dhaka/Geneva, 7 May – The International Organization for Migration (IOM) today launched the World Migration Report 2024 , which reveals significant shifts in global migration patterns, including a record number of displaced people and a major increase in international remittances.  

IOM Director General Amy Pope formally released the report in Bangladesh, which stands at the forefront of migration challenges, including emigration, immigration and displacement.   

“The World Migration Report 2024 helps demystify the complexity of human mobility through evidence-based data and analysis,” IOM Director General Amy Pope said at the launch. “In a world grappling with uncertainty, understanding migration dynamics is essential for informed decision-making and effective policy responses, and the World Migration Report advances this understanding by shedding light on longstanding trends and emerging challenges.” 

The report highlights that international migration remains a driver of human development and economic growth, highlighted by a more than 650 per cent increase in international remittances from 2000 to 2022, rising from USD 128 billion to USD 831 billion. The growth continued despite predictions from many analysts that remittances would decrease substantially because of COVID-19.  

Of that 831 billion in remittances, 647 billion were sent by migrants to low– and middle-income countries. These remittances can constitute a significant portion of those countries' GDPs, and globally, these remittances now surpass foreign direct investment in those countries. 

Highlighting key findings, the report reveals that while international migration continues to drive human development, challenges persist. With an estimated 281 million international migrants worldwide, the number of displaced individuals due to conflict, violence, disaster, and other reasons has surged to the highest levels in modern-day records, reaching 117 million, underscoring the urgency of addressing displacement crises.  

Migration, an intrinsic part of human history, is often overshadowed by sensationalized narratives. However, the reality is far more nuanced than what captures headlines. Most migration is regular, safe, and regionally focused, directly linked to opportunities and livelihoods. Yet, misinformation and politicization have clouded public discourse, necessitating a clear and accurate portrayal of migration dynamics.  

By choosing Dhaka as the report's launch site, IOM not only highlights the country's efforts in supporting vulnerable migrants and fostering pathways for regular migration but also recognizes Bangladesh's important role in shaping global migration discourse and policy.  

As a Global Compact for Safe, Orderly, and Regular Migration Champion country, Bangladesh has demonstrated a strong commitment to addressing migration issues and implementing policies that safeguard migrants' rights. This proactive engagement aligns with IOM's strategic objectives, making Bangladesh an ideal location to launch the 2024 World Migration Report.  

IOM’s World Migration Report, with its innovative digital tools and comprehensive analysis, aims to help dispel myths, provide critical insights, and inspire meaningful action in addressing the challenges and opportunities of human mobility.  

"We hope the report inspires collaborative efforts to harness the potential of migration as a driver for human development and global prosperity," DG Pope said. 

“As one of the GCM champion countries, Bangladesh will not only continue to act upon the pledges it has made for its domestic context but would also take up emerging issues and challenges pertaining to migration and development for informed deliberations at the international level,” said Dr. Hasan Mahmud, Honourable Foreign Minister, Government of the People’s Republic of Bangladesh.

Notes to editors: 

This launch is part of IOM Director General’s first three-day visit to Bangladesh. 

For more information, please contact: 

Marie McAuliffe, World Migration Report Editor at [email protected]  

For media requests: Florence Kim at [email protected]  

RELATED NEWS

Iom's world migration report shows global displacement rising despite covid-19 mobility limits, iom’s world migration report 2020  wins  international  design  awards , world migration report launches dynamic new data visualization platform, world migration report 2020 launched.

Migration updates 

Subscribe to IOM newsletter to receive the latest news and stories about migration.

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• Published: 14 May 2024

2023 summer warmth unparalleled over the past 2,000 years

• Jan Esper   ORCID: orcid.org/0000-0003-3919-014X 1 , 2 ,
• Max Torbenson   ORCID: orcid.org/0000-0003-2720-2238 1 &
• Ulf Büntgen 2 , 3 , 4  

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Including an exceptionally warm Northern Hemisphere (NH) summer 1 ,2 , 2023 has been reported as the hottest year on record 3-5 . Contextualizing recent anthropogenic warming against past natural variability is nontrivial, however, because the sparse 19 th century meteorological records tend to be too warm 6 . Here, we combine observed and reconstructed June-August (JJA) surface air temperatures to show that 2023 was the warmest NH extra-tropical summer over the past 2000 years exceeding the 95% confidence range of natural climate variability by more than half a degree Celsius. Comparison of the 2023 JJA warming against the coldest reconstructed summer in 536 CE reveals a maximum range of pre-Anthropocene-to-2023 temperatures of 3.93°C. Although 2023 is consistent with a greenhouse gases-induced warming trend 7 that is amplified by an unfolding El Niño event 8 , this extreme emphasizes the urgency to implement international agreements for carbon emission reduction.

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Esper, J., Torbenson, M. & Büntgen, U. 2023 summer warmth unparalleled over the past 2,000 years. Nature (2024). https://doi.org/10.1038/s41586-024-07512-y

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The green IT revolution: A blueprint for CIOs to combat climate change

Companies and governments looking to combat climate change are turning to tech for help. AI, new technologies, and some promising tech-driven business models have raised hopes for dramatic progress.

About the authors

This article is a collaborative effort by Gerrit Becker, Luca Bennici, Anamika Bhargava, Andrea Del Miglio , Jeffrey Lewis , and Pankaj Sachdeva, representing views from McKinsey Technology.

While many organizations’ climate goals are lofty, enterprise technology leaders—CIOs, chief digital innovation officers (CDIOs), and chief technology officers (CTOs), among others—have not always succeeded at turning climate ambitions into reality. One of the biggest reasons is that hard facts and clear paths of action are scarce. Misconceptions and misinformation have clouded the picture of what CIOs and tech leaders should do.

We have done extensive analysis of where technology can have the biggest impact on reducing emissions. To start, we divided technology’s role into two primary types of activities:

• offense—the use of technology and analytics to cut emissions by reducing (improving operational efficiency), replacing (shifting emission-generating activities to cleaner alternatives), and reusing (recycling material)
• defense—the actions IT can take to reduce emissions from the enterprise’s technology estate

Scope of the McKinsey analysis

McKinsey’s emissions analysis for this report focuses on enterprise technology emissions, which are the business IT emissions from the hardware, software, IT services, enterprise communications equipment, mobile devices, fixed and mobile network services, and internal technology teams that a company uses for its own operations and that a CIO has control over. These include the emissions related to the full life cycles of the products and services that an enterprise IT function uses, including their development, delivery, usage, and end of life (exhibit). Our internal services emissions' analysis assumes around 40 percent of IT workers are working from home.

The analysis does not include the emissions from the technology products and services that a company is selling (such as data center capacity sold by hyperscalers), operational technology devices (such as sensors and point-of-sale systems), and cryptocurrency mining.

The defense activities are where the CIO, as the head of IT, can act independently and quickly. This article focuses on defense, specifically the IT elements over which a CIO has direct control. We examined emissions from use of electricity for owned enterprise IT operations, such as the running of on-premises data centers and devices (classified as scope 2 by the Greenhouse Gas Protocol 1 Greenhouse Gas Protocol: Technical Guidance for Calculating Scope 3 Emissions: Supplement to the Corporate Value Chain (Scope 3) Accounting & Reporting Standard , World Resources Institute & World Business Council for Sustainable Development, 2013. Scope 1 emissions are direct emissions from the activities of an organization or under their control, including fuel combustion on site such as gas boilers, fleet vehicles, and air-conditioning leaks; scope 2 emissions are from electricity purchased and used by the organization; and scope 3 emissions are all indirect emissions not included in scope 2 that occur in the value chain of the reporting company, including both upstream and downstream emissions. ), and indirect emissions from technology devices that the CIO buys and disposes of (scope 3). 2 These calculations do not include emissions from technology-driven services sold, such as cloud capacity. (See sidebar, “Scope of the McKinsey analysis.”)

What the facts say

Our analysis has uncovered several facts that contravene some commonly held views about enterprise technology emissions. These facts involve the significant amount of tech-related emissions, the share of emissions from end-user devices, the variety of mitigation options available, and the favorable impact of shifting to cloud computing.

Enterprise technology generates significant emissions

Enterprise technology is responsible for emitting about 350 to 400 megatons of carbon dioxide equivalent gases (CO 2 e), accounting for about 1 percent of total global greenhouse gas (GHG) emissions. At first blush, this might not seem like a lot, but it equals about half of the emissions from aviation or shipping and is the equivalent of the total carbon emitted by the United Kingdom.

The industry sector that contributes the largest share of technology-related scope 2 and scope 3 GHG emissions is communications, media, and services (Exhibit 1). Enterprise technology’s contribution to total emissions is especially high for insurance (45 percent of total scope 2 emissions) and for banking and investment services (36 percent).

This amount of carbon dioxide and equivalent gases is a significant prize for companies under increasing pressure to cut emissions. Progress on climate change requires action on many fronts, and enterprise technology offers an important option that CIOs and companies can act on quickly.

You’re invited

To a McKinsey Technology webinar on the critical role of technology in building a sustainable enterprise on October 25, 9:30–10:30am ET.

The biggest carbon culprit is end-user devices, not on-premises data centers

End-user devices—laptops, tablets, smartphones, and printers—generate 1.5 to 2.0 times more carbon globally than data centers (Exhibit 2). 3 On-premises and co-located data centers used by enterprises, not including data center capacity sold by hyperscalers. One reason is that companies have significantly more end-user devices than servers in on-premises data centers. In addition, the devices typically are replaced much more often: smartphones have an average refresh cycle of two years, laptops four years, and printers five years. On average, servers are replaced every five years, though 19 percent of organizations wait longer. 4 Rhona Ascierto and Andy Lawrence, Uptime Institute global data center survey 2020 , Uptime Institute, July 2020.

More worrisome, emissions from end-user devices are on track to increase at a CAGR of 12.8 percent per year. 5 End-user computing market: Growth, trends, COVID-19 impact, and forecasts (2022–2027) , Mordor Intelligence, January 2022. Efforts to address this could target the major causes of emissions from these devices. About three-fourths of the emissions comes from manufacturing, upstream transportation, and disposal. A significant source of these emissions is the semiconductors that power the devices.

Plenty of low-cost/high-impact options exist, starting with improved sourcing

We have found that when it comes to going green, many CIOs think in terms of investments needed to replace items or upgrade facilities. Our analysis, however, finds that CIOs can capture significant carbon benefits without making a significant investment—and in some cases can even save money (Exhibit 3).

Overall, for example, 50 to 60 percent of emissions related to end-user devices can be addressed through sourcing changes, primarily by procuring fewer devices per person and extending the life cycle of each device through recycling. These options will not require any investment and will lower costs, though companies may want to evaluate the impact on employee experience.

In addition, companies can more aggressively recycle their devices; 89 percent of organizations recycle less than 10 percent of their hardware overall. 6 Sustainable IT: Why it’s time for a green revolution for your organization’s IT , Capgemini Research Institute, 2021. CIOs can put pressure on suppliers to use greener devices, especially as companies in the semiconductor sector are already increasing their commitments to emission reduction. Further low-cost, high-impact actions include optimizing business travel and data center computing needs, as well as increasing the use of cloud to manage workloads.

Moving to cloud has more impact than optimizing data centers

Optimizing an on-premises data center’s power usage effectiveness (PUE) 7 PUE describes how efficiently a computer data center uses energy, expressed as the ratio of total facility energy to IT equipment energy. is expensive and results in limited carbon abatement. If a company were to double what it spends on infrastructure and cloud to reduce PUE, it would cut carbon emissions by only 15 to 20 percent. Structural improvements in data centers and optimized layout can help, but the impact is limited, and many companies have already implemented them. More aggressive measures, such as moving data centers to cooler locations or investing in new cooling tech, are prohibitively expensive.

A more effective approach is to migrate workloads to the cloud. Hyperscalers (also known as cloud service providers) and co-locators are investing significantly to become greener through measures such as buying green energy themselves and investing in ultra-efficient data centers with a PUE equal to or less than 1.10, compared with the average PUE of 1.57 for an on-premises data center. 8 “Uptime Institute 11th annual Global Data Center Survey shows sustainability, outage, and efficiency challenges amid capacity growth,” Uptime Institute, September 14, 2021. (We estimate that companies could achieve just a 1.3 PUE score for their data center if they invested nearly 250 percent more, on average, over what they currently spend for their data centers and cloud presence.)

With thoughtful migration to and optimized usage of the cloud, companies could reduce the carbon emissions from their data centers by more than 55 percent—about 40 megatons of CO 2 e worldwide, the equivalent of the total carbon emissions from Switzerland.

Three steps to take now

With companies and governments under intensifying pressure to cut carbon emissions and with technology playing a key role in delivering on those goals, CIOs will find themselves on the front lines. The challenge will be to reduce IT’s carbon footprint while delivering high-quality, low-cost technology services to customers and employees.

On average, completion of the defensive steps might take three to four years. However, CIOs who act decisively and precisely can achieve 15 to 20 percent of carbon reduction potential in the first year with minimal investment.

CIOs can choose from among a wide array responses, particularly in conjunction with the CEO and the board. However, three measures they can take right now will prepare the organization for longer-term efforts. These measures involve sourcing strategies, key metrics, and a performance management system.

The net-zero transition: What it would cost, what it could bring

Move now on sourcing strategies.

Far and away the fastest and most effective defensive measure for reducing IT carbon emissions is to revise policies for technology sourcing. Optimizing the number of devices in line with standards followed by companies in the top quartile 9 Top quartile in terms of the ratio of devices to people is derived from the number of devices per person. Our analysis uses McKinsey Digital’s Ignite solutions and 2020 data. would reduce about 30 percent of end-user-device emissions, the amount of carbon emitted by Hong Kong. For example, top-quartile companies have one printer for every 16 people in the workplace; the overall average is one printer per eight people.

This sourcing shift does not necessarily lead to a degradation in user experience, because the rollout of 5G and increasingly advanced processing and compute power allow the main processing function to happen at the server. Therefore, devices can be less powerful and consume much less energy. Essentially, this is a software-as-a-service (SaaS) model where high-end and user-friendly experiences happen on the server, not the device. The effectiveness of this approach will depend on having stable networks, less resource-intensive coding at the device level, edge computing capabilities, and shifts of offerings to more efficient platforms (for example, cloud).

As part of this effort, the CIO and the business’s head of procurement will need to collaborate on reviewing and adjusting device refresh timelines and device-to-person ratios, as well as adjusting the basis for purchasing decisions. Procurement generally relies on cost/benefit calculations, and rightly so. That approach will need to expand to account for carbon dioxide emissions. The spirit of collaboration should extend to suppliers as well, with the parties working together to formulate plans that provide the greatest benefits for all.

A more thoughtful sourcing strategy extends beyond end-user devices. CIOs, for example, should look for green sources of the electricity IT uses. When these sources are unavailable, CIOs can direct procurement to power purchase agreements to offset carbon use. CIOs can also set green standards for their vendors and suppliers, requiring GHG emissions disclosures and incorporating them into their criteria for purchase decisions.

Establish a green ROI metric for technology costs

Any real progress on green technology can happen only when companies measure their “green returns.” But today, most green metrics omit cost and savings, which ultimately makes them impractical. A better metric focuses on cost per ton of carbon saved (accounting for costs saved as well). Sophisticated models calculate emissions throughout the full life cycle, including production, transportation, and disposal.

CIOs can further assess suppliers, manufacturers, and service providers based on how advanced they are in recycling and refurbishing electronics; designing circular components; extending product life cycles with better design, higher-quality manufacturing, and more robust materials; offering repair services; and reselling to consumers.

Decisions about IT spending need to consider a range of factors, including technical debt abatement and business strategy. Along with these factors, companies should institutionalize a green ROI metric that is transparent to everybody in the business as an element in IT decision making, including in requests for proposals (RFPs). Doing so will enable companies to better understand the true impact their technology is having on carbon emissions.

Put in place green measurement systems

Establishing a green ROI metric is only a start. CIOs need to establish a baseline of performance, measure progress against the baseline, and track impact in near real time, much as companies track real-time computer and network usage for applications in the cloud. This kind of measuring system ensures that CIOs know what’s working and what isn’t, so they can adjust quickly.

In practice, implementing green measurement can be challenging. Some companies have spent a year measuring their carbon footprint, ending up with an outdated analysis. This tends to happen when companies are determined to measure every bit of carbon emitted, a praiseworthy but time-consuming effort. CIOs can make substantial progress by instead prioritizing measurement where the impact is highest, such as tracking the number of end-user devices purchased and in use, the current duration of use for each device, and the ratio of devices per user. Another way CIOs can make quick progress is to embed emissions- and power-monitoring capabilities into large technology assets and work with external providers, such as electricity companies, to track usage in real time.

Effectively combating climate change won’t happen through one or two big wins; those don’t exist yet. To have real impact, companies and governments will need to act in many areas. Technology has a huge role to play in many of these areas, but CIOs and tech leaders need to act quickly and decisively.

This article is the first in a series about how CIOs can reduce emissions. The next article will explore how CIOs can drive the business’s sustainability agenda by playing offense and implementing reduce, replace, and reuse levers to decarbonize.

Gerrit Becker is an associate partner in McKinsey’s Frankfurt office, Luca Bennici is an associate partner in the Dubai office, Anamika Bhargava is a consultant in the Toronto office, Andrea Del Miglio is a senior partner in the Milan office, Jeffrey Lewis is a senior partner in the New Jersey office, and Pankaj Sachdeva is a partner in the Philadelphia office.

The authors wish to thank Bernardo Betley, Arjita Bhan, Raghuvar Choppakatla, Sebastian Hoffmann, Abdelrahman Mahfouz, Tom Pütz, Jürgen Sailer, Tim Vroman, Alice Yu, and Gisella Zapata for their contributions to this article.

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A systematic review of climate migration research: gaps in existing literature

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• Volume 2 , article number  47 , ( 2022 )

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Climatic disasters are displacing millions of people every year across the world. Growing academic attention in recent decades has addressed different dimensions of the nexus between climatic events and human migration. Based on a systematic review approach, this study investigates how climate-induced migration studies are framed in the published literature and identifies key gaps in existing studies. 161 journal articles were systematically selected and reviewed (published between 1990 and 2019). Result shows diverse academic discourses on policies, climate vulnerabilities, adaptation, resilience, conflict, security, and environmental issues across a range of disciplines. It identifies Asia as the most studied area followed by Oceania, illustrating that the greatest focus of research to date has been tropical and subtropical climatic regions. Moreover, this study identifies the impact of climate-induced migration on livelihoods, socio-economic conditions, culture, security, and health of climate-induced migrants. Specifically, this review demonstrates that very little is known about the livelihood outcomes of climate migrants in their international destination and their impacts on host communities. The study offers a research agenda to guide academic endeavors toward addressing current gaps in knowledge, including a pressing need for global and national policies to address climate migration as a significant global challenge.

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Introduction

Population displacement can be driven by climatic hazards such as floods, droughts (hydrologic), and storms (atmospheric), and geophysical hazards such as earthquakes, volcanic eruptions, and tsunami (Smith and Smith 2013 ). The interactions between natural hazard events, and social, political, and human factors, frequently act to intensify the negative effects of climatic and geophysical hazards, leading to political and social unrest, increased social vulnerability, and human suffering. As a consequence of these adverse effects, people migrate from their native land, causing stress, uncertainty, and loss of lives and properties. However, such migration can also have positive impacts on migrants’ lives. For example, migrants may be able to diversify their livelihood and have greater access to education or healthcare.

In 2020, 30.7 million people from 149 countries and territories were displaced due to different natural disasters. Among them, climatic disasters were solely responsible for displacing 30 million people within their own country, with the highest recorded displacement occurring in 2010 when 38.3 million people were displaced (IDMC 2021a ; IOM 2021 ). It is difficult to estimate the actual number of people that moved due to the impacts of climate change (Mcleman 2019 ), because peoples’ migration decisions are triggered by a range of contextual factors (de Haas 2021 ). Nevertheless, the Internal Displacement Monitoring Centre (IDMC) states that approximately 283.4 million people were displaced internally between the years 2008 and 2020 because of climatic disasters across the globe (Table 1 ). This number represents almost 89% of the total disaster-induced displacement that occurred during this timeframe (IDMC 2021a ).

People who move from their homes due to climate-driven hazards are described in a range of ways, including climate migrants, environmental migrants, climate refugees, environmental refugees, and so on (Perkiss and Moerman 2018 ). The process of migration related to climate-driven hazards is variously described as environmental migration, environmental displacement, climate-induced migration or climigration (Bronen 2008 ).

In this research, we focus on climate-induced migration more specifically induced by slow-onset climatic disasters (sea-level rise, drought, salinity etc.), rapid onset extreme climatic events (storms, floods etc.), or both (precipitation, erosion etc.). This study investigates how climate change-induced migration studies are framed in the existing literature and identifies key gaps in the published literature.

There is a significant ongoing debate about the links between climate change and human migration in the academic literature. Some researchers strongly believe that climate change directly causes people to move, whereas the others argue that climate change is just one of the contextual factors in peoples’ migration decisions (Laczko and Aghazarm 2009 ). Although there are scholarly opinions that call into question climate change as a primary cause of migration (Black 2001 ; Black et al. 2011 ; McLeman 2014 ), there is also evidence that climate change causes severe environmental effects and exacerbates the vulnerabilities of people that force them to leave their place of living (Bronen and Chapin 2013 ; Laczko and Aghazarm 2009 ; McLeman 2014 ).

Moreover, the relationship between the adverse effects of climate change and different types of human mobility (migration, displacement, or planned relocation) has become increasingly recognized in recent years (Kälin and Cantor 2017 ). It is assumed in general that the number of climate displaced people is likely to increase in future (Mcleman 2019 ; Wilkinson et al. 2016 ), and climate change could permanently displace an estimated 150 million to nearly 1 billion people as a critical driver by 2050 (Held 2016 ; Perkiss and Moerman 2018 ). As the number of climate migrants increases rapidly in some areas of the world (IDMC 2017 ), it is now confirmed as a significant global challenge (Apap 2019 ) and recognized as a considerable threat to human populations (Ionesco et al. 2017 ).

Climate migration has multifaceted impacts on peoples’ livelihoods. Being displaced from their home, people migrate within their own country, described as internal migration, or across borders to other countries known as international migration. Internal movements of climate migrants occur mostly to nearby major cities or large urban centers (Poncelet et al. 2010 ). Climate migrants who try to move internationally are significantly challenged by two different security problems. Firstly, they cannot live in their own homeland because of worsening climatic impacts and are forced to leave their ancestral land. Secondly, they cannot move to other countries quickly to find a safer place because, according to international law, climate migrants are not refugees and they are not supported by the UN Refugee Convention or any international formal protection policies (Apap 2019 ; Mcleman 2019 ). In this situation, they live with significant livelihood uncertainty. The United Nation’s Sustainable Development Goals (SDGs) and the Sendai Framework for Disaster Risk Reduction (SFDRR) recognize them as a key group that is highly exposed and vulnerable because of their circumstances (Ionesco et al. 2017 ). Hence, policy development to address complex climate migration issues has become an emerging priority around the globe (Apap 2019 ).

In order to address this global challenge, there has been growing academic and policy attention focused on regional (Kampala Convention-2009 by African Union), national (Nansen Initiative—2012 by Norway and Switzerland), and international (Global Compact for Safe, Orderly and Regular Migration- 2018 by United Nations) levels of climate-induced migration in recent years. Myers’s ( 2002 ) seminal article signposted environmentally driven migration as one of the most significant challenges of the twenty-first century, and later, similar assumptions were made by Christian Aid (Baird et al. 2007 ), IOM (Brown 2008 ), and Care International (Warner et al. 2009 ). Such predictions led to a proliferation of the academic discourse on migration, focused on national and international security, policy frameworks, and human rights (Boncour and Burson 2009 ). Other studies have focused on vulnerability assessment, risk reduction, adaptation, resettlement, relocation, sustainability, and resilience, considering pre-, during and post-disaster circumstances of climate migration (Bronen 2011 ; Bronen and Chapin 2013 ; IDMC 2019 ; IOM 2021 ; King et al. 2014 ).

This research contributes to the discourse by identifying the gaps in the published literature regarding climate migration. A systematic literature review was undertaken to shed light on the current extent of academic literature, including gaps in knowledge to develop a climate migration research agenda. Two notable review papers provided a solid foundation for this endeavor. First, Piguet et al. ( 2018 ) developed a comprehensive review of publications on environment-induced migration from a global perspective based on a bibliographic database—CliMig. Their detailed mapping of environmentally induced migration research focused on five categories of climatic hazards (droughts, floods, hurricanes, sea-level rise, and rainfall); however, it did not include salinity and erosion which are also climate-driven and has direct effects on internal and international migration (Chen and Mueller 2018 ; Mallick and Sultana 2017 ; Rahman and Gain 2020 ).

The second key review paper was by Obokata et al. ( 2014 ), which provided an evidence-based explanation of the environmental factors leading to migration, and the non-environmental factors that influence the migration behaviors of people. Their scope of analysis was limited to international migration and excluded other types of migration, such as internal climate-induced migration.

Although migration, or more specifically environmental migration, was occurring over many decades of the twentieth century, the IPCC First Assessment report was released in 1990, which presented the first indications of the risks of climate change-induced human movement (IPCC 1990 ). This milestone report then stimulated the academic discourse, and consequently, a rapid increase in climate migration publication resulted. For this reason, the current study undertook a systematic review of literature across three decades beginning in 1990 and ending in 2019. This study aims to understand how the published literature has framed the climate-induced migration discourse. This paper identifies the key gaps in existing scholarship in this field and proposes a research agenda for future consideration on current and emerging climate migration issues.

In the following section, we outline the systematic review method and identify how journal articles were searched, selected, reviewed, and analyzed. In the next section, we present the results of this study. Results are organized into four subsections that illustrate the reviewed literature in the following ways—spatial and temporal trends, disciplinary foci, triggering forces of migration, and other key issues. Finally, we conclude by identifying research gaps, addressing the limitations of this study, and presenting a research agenda.

Methodology

We have adopted a systematic review methodology for this study because it provides an …overall picture of the evidence in a topic area which is needed to direct future research efforts (Petticrew and Robert 2006 ). Systematic reviews reduce the bias of a traditional narrative review, although it is challenging to eliminate researcher bias while interpreting and synthesizing results (Doyle et al. 2019 ). It also limits systematic bias by identifying, evaluating, and synthesizing all relevant studies to answer specific questions or sets of questions, and produces a scientific summary of the evidence in any research area (Petticrew and Robert 2006 ). Moreover, systematic reviews effectively address the research question and identify knowledge gaps and future research priorities (Mallett et al. 2012 ). We have adopted this approach following the methodology developed by Berrang-Ford et al. ( 2011 ) which was tested in the field of environmental and climate change studies, with measurable outcomes. We have conducted the review following these four steps—article search, selection, review, and analysis (Fig.  1 ).

Systematic review flowchart

Article search

We conducted a comprehensive literature search to identify the published academic literature on climate-induced migration to develop a clear understanding of this field of study. We identified sixteen commonly used keywords to search for articles that are predominantly used in the literature. ProQuest central database was selected and used in consultation with a skilled subject librarian to search for the relevant articles for this study. We conducted this literature search in July 2019 using the key thesaurus terms, presented in Table 2 . All keywords were then searched individually in the publication’s title and abstract. We only considered English language peer-reviewed articles for this study, published between the years 1990 and 2019 (up to June).

Article selection

The main purpose of this process was to ensure the selection of appropriate literatures for further analysis. We approached the Preferred Reporting Items for Systematic Reviews and Meta Analyses (PRISMA), a systematic evaluation tool, which was also used by Huq et al. ( 2021 ). In stage one of the selection process, 277 articles were counted based on our search criteria. In stage two, we excluded 25 duplicates, and 252 articles remained for further assessment. In the third and final stage of the detailed assessment of each paper, we identified a further 91 publications that were not relevant to our study but appeared in our searched list because search terms were briefly mentioned in their title and/or abstract without being described in further detail. As these articles did not fit with the aim and content of this research, we excluded those 91 and selected a final 161 articles for this study.

Article review

All the selected articles were then considered for detailed review in order to achieve the purpose of the study. A questionnaire (Online Attachment—A) was developed partially following Berrang-Ford et al. ( 2011 ); Obokata et al. ( 2014 ) and Piguet et al. ( 2018 ) to investigate how climate migration studies are framed in the published literature. Then each article was reviewed in detail in response to the individual parameters of the questionnaire such as general information ( article title, authors name, publication year, journal, discipline, content ), methodological approach ( qualitative, quantitative, mixed ), focused study areas ( country, climatic zones ), source of migrants ( rural, urban ), migration types ( internal, international ), impacts of climate migration ( social, economic, political, health, cultural, environmental, security ), causes of migration ( climatic: flood, sea-level rise, drought etc ., other: socio-economic, political, cultural ), target communities ( displaced community, receiving community ), and livelihoods ( housing, income, employment, etc . ) of climate migrants described in the publications.

Article analysis

All the data were recorded in Microsoft Office Excel spreadsheets. Relevant data for each parameter were filtered, analyzed, and summarized using the necessary Excel tools. Referencing was compiled through Mendeley Desktop.

Spatial and temporal trend

General information.

In this section, the publication date of the reviewed articles was used in order to identify the development of the academic discourse in climate migration studies over the last three decades (1990–2019). Results show the increasing focus of academic attention on this area of research over that timeframe. The study found only four publications between the years 1990 and 1999. During 2000–2009, an additional 16 articles were published, which was followed by an almost 90 percent (141 publications) increase in reviewed articles over the period of 2010–2019 (Table 3 ).

Reviewed study areas

In 84 reviewed articles, the study reported research focused on a particular location, and in some cases, they considered two or more areas for their research. Therefore, multiple counting for each study has been considered, which represents all the continents except Antarctica. The analysis shows that Asia (38%) is the continent with the greatest number of climate migration studies, followed by Oceania (20%), North America (17%), and Africa (14%). In contrast, Europe and South America have received less attention, with 7% and 5%, respectively. Table 4 presents the distribution of study areas by continent focused on the reviewed papers.

Climatic zones of the reviewed studies

This study identified the climatic zones of the study areas in order to find out which zones are most commonly studied among the reviewed studies. We adopted the climatic zones of the world from Peel et al. ( 2007 ), which is the updated version of Koppen’s climate classification, and categorizes the world climate into five major zones, i.e., (i) tropical, (ii) arid, (iii) temperate, (iv) cold, and (v) polar. This review shows that 86 publications mentioned their study areas, equating to 54% of the total reviewed papers. Among them, 81% referred to a specific region as their study area. The study areas were then classified into the above-mentioned climatic zones with one reference offered randomly for each country as an example of the range of research that has been conducted.

This study reveals that 49% of this group (among 81%) focused on tropical climatic areas such as Bangladesh (Islam et al. 2014 ), Cambodia (Jacobson et al. 2019 ), Kiribati (Bedford et al. 2016 ), Papua New Guinea (Connell and Lutkehaus 2017 ), Philippines (Tanyag 2018 ), Tuvalu (Locke 2009 ), and Vanuatu (Perumal 2018 ) among others, and 16% focused on arid climatic zones such as African Sahel (McLeman and Hunter 2010 ), Israel (Weinthal et al. 2015 ), Peru (Scheffran 2008 ), and Senegal (Nawrotzki et al. 2016a , b ). In addition to these, 13% of authors focused on temperate regions, i.e., Mexico (Nawrotzki et al. 2016a , b ), Nepal (Chapagain and Gentle 2015 ), Taiwan (Kang 2013 ), UK (Abel et al. 2013 ), and the USA (Rice et al. 2015 ) for their study and 3% focused on cold climatic areas, i.e., Alaska: USA (Marino and Lazrus 2015 ), Canada (Omeziri and Gore 2014 ), and northern parts of China (Ye et al. 2012 ). No studies were found based on polar regions (Fig.  2 ). Some studies did not specify a region or country of study but instead focused on broader regions such as Africa (White 2012 ), Asia–Pacific (Mayer 2013 ), Europe (Werz and Hoffman 2016 ), Latin America (Wiegel 2017 ), and Pacific (Hingley 2017 ).

Climatic zones of the reviewed study areas-adopted from Peel (2007)

Migration types and sources of climate migrants

Migration types here refer to whether migration was internal (within a country or region) or international (across borders), and sources of climate migrants refer to people from rural or urban source regions. Most authors (73%) mentioned nothing regarding migration types, but a quarter (27%) explicitly discussed internal or international migration. Among them, 11% described climate migration within countries and 10% investigated cross-border migration. Some authors (6%) were concerned with both internal and international climate migration. Source regions for climate migrants were not often considered, with only 19 publications mentioning the origin of migrants. Among these, 11 articles stated that migration occurred from rural areas, and two publications discussed migration from urban areas. Also, six articles described climate migration from both rural and urban areas.

Disciplinary foci

Research discipline.

This study reveals that climate migration studies are becoming more focal issues in different research disciplines that include more than 40 subject areas. Hence, we developed a typology for the reviewed articles based on the relevant research themes. The typology consists of six research disciplines, each of which includes different subjects, as follows.

Social sciences: Social sciences, Sociology, Political Science, International Relations, Comprehensive Works, Population Studies, Anthropology, Social Services and Welfare, History, Philosophy, Ethnic Interests, Civil Rights, Women's Studies

Geography and environment: Meteorology, Environmental Studies, Energy, Conservation, Earth Sciences, Geography, Agriculture, Geology, Biology, Archaeology, Pollution

Business studies and development: Management, Business and Economics, International Commerce, International Development and Assistance, Economics, Insurance, Investments, Accounting

Law, policy, and planning: Law, Military, Civil Defense, Criminology and Security, Environmental policy

Health and medical science: Public Health, Psychology, Medical Sciences, Physical Fitness, and Hygiene

Other: Literature, Library and Information Sciences, Physics, Technology

Among the reviewed publications, some articles were discussed from the perspective of one particular discipline, while others came from two or more disciplines. Therefore, multiple counting for each discipline was considered during the analysis. The study reveals that Social Science covers the highest percentage of publications (41%), followed by Geography and Environment (30%), Business Studies and development (10%), Law, policy and planning (9%), and Health and medical science (7%). Only 2% of publications are not covered by any of these disciplines.

Primary research themes

The authors discussed a diverse range of themes in the reviewed articles. Key themes have been classified into eight categories based on their topics and focusing subjects. Some of the publications focused on multiple themes, which were counted separately under each theme. Most of the authors (27%) focused on Politics and policy issues, and almost a fifth (18%) of total articles focused on the themes of population, health, and development issues. Human rights, conflicts, and security issues were discussed in 16% of papers, and climate, vulnerability, adaptation, and resilience topics were the focus of 12% of publications. In 11% of publications, the authors focused on identity and cultural issues, and socio-economic topics comprised a further 9% of the total. Environmental issues were discussed by 4% of reviewed articles and 3% of publications did not fit into any of the above categories and are described as Other.

Methodological approaches

This review identified that researchers applied both qualitative and quantitative methods in climate migration research. A total of 82% of the reviewed articles used qualitative methodologies, and 9% quantitative. In addition to these, 9% of articles used mixed methods in climate migration research. Of those who used qualitative studies, most were review-based (86%), comprising systematic review, empirical evidence-based review, critical synthesis review, critical discourse review, and policy review. Only 14% of qualitative studies used interview methods (7%), case studies (6%), and focus group discussion (1%). Data sources reported in the reviewed literature for the quantitative research included secondary data (73%), historical data (13%), remote sensing data (7%), and survey data (7%).

Triggering forces of migration

Climatic causes of migration.

The reviewed publications outlined a range of different causes of climate migration. This study reveals nineteen climate-related causes of migration. We merged these causes into eight categories, defined as (i) climate change (climate change, global warming, temperature, environmental change, climate-induced natural disaster, meteorological events, extreme weather, heatwave), (ii) flood, (iii) sea-level rise (sea-level rise, melting glacier), (iv) drought (drought, desertification), (v) storm (storm, cyclone, hurricane, typhoon), (vi) salinity (salinity, tidal surge), (vii) precipitation-induced landslide, and (viii) erosion (coastal erosion, river erosion). “Climate change” is defined as a separate category because some publications named climate change as an overarching driver of migration, rather than specifying any particular hazard. In 70 publications, authors mentioned particular climatic events that were solely responsible for human migration, and 53 of these articles predominantly identified climate change as the main driver of migration, followed by sea-level rise (6), drought (4), flood (3), storm (2), and precipitation-induced landslide (2). In the remaining articles, scholars identified two or more climatic events that were collectively responsible for human displacement. Based on these articles, multiple counting for each climatic event was considered and the results show that climate change was the most commonly cited cause in 126 articles, along with other climatic causes. The authors also identified sea-level rise, drought, flood, and storms as the significant drivers of peoples’ migration along with other climatic drivers, which were mentioned in 51, 46, 44, and 43 articles, respectively. Precipitation-induced landslide and erosion were recognized in 17 and 12 articles, respectively, as the causes of human displacement, whereas eight articles identified salinity as the main reason.

Influencing causes of migration

Although this review was focused on identifying the climatic causes of human displacement, some other causes emerged during the analysis that also influence migration. In 68 publications, economic, social, environmental, political, cultural, and psychological causes were stated as drivers of migration, in addition to the climatic causes. Among these, economic causes (32%) have been identified as the most common driver, followed by social (25%) and environmental (22%) causes. Some articles described political causes (16%), and the remainder mentioned cultural (3%) and psychological (1%) drivers of migration.

Other key issues

• Impacts of climate migration

One of the key findings of this review concerns the impacts of climate migration. In 48 publications, authors described a range of different impacts caused by climate migration, such as social, economic, political, health, cultural, environmental, and security. All the impacts were identified based on the location of climate migrants which are classified into the following three categories: (i) impacts on the place of origin, (ii) impacts on the place of destination, and (iii) impacts on both origin and destination. The review demonstrates that the impacts of climate migration were more frequently identified for the place of origin rather than for the destination. In the place of origin, authors discussed the economic, social, and cultural impacts, compared to political, security, health, and environmental impacts. In contrast, in the destination, scholars were more focused on security and cultural impacts. Overall, security, cultural and economic impacts were the most frequently discussed themes by the authors of reviewed literature in comparison with other impacts (Table 5 ).

Discussed communities

More than half of the reviewed articles ( N  = 81) described climate migrants and/or their receiving communities. In most of the discussions, authors talked about both displaced and host communities together (57%). In more than two-fifths of articles, they considered only displaced communities (42%). In contrast, none of the authors of the reviewed literature discussed host communities in detail in their publications, except Dorent ( 2011 ). Only a few authors briefly mentioned host communities during the discussion of climate migration impacts.

Livelihoods of climate migrants

This review demonstrates that the overall livelihood of climate migrants has not been a key focus in any of the reviewed literature. However, a few separate parameters of livelihoods, including housing, income and employment, health, access to resources, and education were mentioned in 23 articles. The analysis shows that the livelihoods of migrants in their place of origin (71%) were more likely to be considered compared to their destination (11%). In some articles (18%), authors addressed the livelihoods of climate migrants considering both their place of origin and destination. In total, all the articles which considered livelihoods had a specific focus on internal migration, and none mentioned the livelihoods of climate migrants in terms of international migration.

Discussion and research gaps

Climate change-induced migration is neither new (Nagra 2017 ), nor a future hypothetical phenomenon—it is a current reality (Coughlin 2018 ). This review provides a comprehensive analysis of how this field of study is framed in the existing literature. The academic discourse on human migration due to climate change is suggestive of a long-standing causal connection, which is hard to dissociate (Milán-García et al. 2021 ; Parrish et al. 2020 ; Piguet et al. 2011 ).

The review of spatial and temporal trends of climate-induced migration studies illustrates the growth in the field since the release of 1st IPCC report in 1990. In addition, this review has explored some basic questions that are useful to guide future research in this field of study, for instance, which study areas have received greater or lesser focus? Where are these study areas located in relation to global climatic zones? How are people migrating, i.e., internally, or internationally? What are the spatial sources of climate-induced migrants, i.e., rural, or urban environments?

This review also demonstrates that the expansion of climate migration research increased rapidly after 2000, although the studies in this field began before 2000 (Table 3 ). It denotes that the global academia and policymakers have emphasized their focus on this topic in recent decades (Milán-García et al. 2021 ; Piguet et al. 2011 ). Moreover, this review identifies the Asia–Pacific region as the global ‘hotspot’ of climate migration research (Table 4 ). This reflects the IDMC ( 2019 ) report that states more than 80% of the total displacement between 2008 and 2018 occurred within this region. Moreover, a significant proportion of global environmental displacement will continue to occur in the Asia–Pacific region (Mayer, 2013 ). Therefore, this region could be considered as a critical ‘living laboratory’ for future climate migration research.

Climate migration is mostly occurring internally (IDMC 2021a ; Laczko and Aghazarm 2009 ), and in recent years, it has been widely acknowledged in the policy areas (Fussell et al. 2014 ; The World Bank 2018 ). Nevertheless, this study reveals that only a quarter of the reviewed studies for example, Chapagain and Gentle ( 2015 ), Islam et al. ( 2014 ), and Prasain ( 2018 ) have considered the migration types (internal or international) and sources (rural or urban) of climate migrants in their research. Thus, this review identifies the gap and need for contributions to the academic discourse that investigate migration types, the origin of migrants, and their patterns of migration.

The review of the disciplinary foci of climate-induced migration literature reveals that a broader range of disciplines are now focusing on this research topic, which suggests that greater interdisciplinarity is developing in the discourse. IDMC ( 2021b ) data presented in Table 1 show that climate-induced disasters are displacing millions of people every year, but surprisingly none of the reviewed publications appeared under the subject category of disaster management in the database. This reflects the emergent nature of the academic discourse on climate migration and disaster management, which includes recent studies by Ye et al. ( 2012 ), Tanyag ( 2018 ), and Hamza et al. ( 2017 ). In addition, politics and policy issues regarding climate migration were discussed by scholars; however, no country-specific policies were found during the review that considered both the origin and host communities of climate migrants.

Campbell ( 2014 ) argues that there is insufficient empirical evidence within climate migration research. However, this review reveals that research in this area has been undertaken using a range of methodologies, from qualitative (review, case study, interview, focus group discussion etc.) to quantitative (based on survey data, secondary data, historical data, and remote sensing data), which has produced a strong foundation of work to guide future pathways for interdisciplinary climate migration research. A significant proportion of the research to date has been review-based. Also, there is a lack of empirical studies in this research field that consider the application of geographic information system and remote sensing.

It is clear from reviewing the triggering forces of climate-induced migration literature that climatic events are dominantly responsible for climate migration, which is supported by Rahman and Gain ( 2020 ), Connell and Lutkehaus ( 2017 ), Gemenne ( 2015 ), and Kniveton et al. ( 2012 ). Despite this, there are some other influencing push and/or pull factors such as socio-economic, political, cultural, etc., which are likely to compound (or be compounded by) climate impacts, to trigger the migration process (Black et al. 2011 ; de Haas 2011 , 2021 ; Fussell et al. 2014 ). While there remains ample anecdotal evidence of the relationship between climate change impacts and migration, the specific reasons for people to decide to migrate are interwoven with indirect pressures, such as livelihood disruption, poverty, war, or disaster (Werz and Hoffman 2016 ). Moreover, why people choose to stay at their places is also essential in the context of creeping environmental and climate-induced migration (Mallick and Schanze 2020 ).

One of the other key issues reviewed in this study is that the literature to date fails to build an understanding of the impacts of climate migration on both the origin (source regions) and destination of the climate migrants. There are very few studies such as Comstock and Cook ( 2018 ), Maurel and Tuccio ( 2016 ), Pryce and Chen ( 2011 ), Rahaman et al. ( 2018 ), Rice et al. ( 2015 ), and Schwan and Yu ( 2017 ) that investigate different aspects of socio-economic impacts (housing, health, social, economic, etc.) of climate migration in the destination region, and this presents a clear gap in knowledge that requires further study. Also, no current research has been identified during the review that focused on the environmental impacts of climate migration.

In addition, this review identifies that there was less attention paid to the impacts of climate migration on host communities compared to displaced populations in their new locations. Given that migration will continue to increase globally, there is likely to be a growing need to understand the range of potential impacts on host communities. Although some countries and regions are developing policies to manage internal migration, there are no formal protection policies for cross-border climate migration (Nishimura 2015 ; OHCHR 2018 ; Olsson 2015 ; Zaman 2021 ). Therefore, policy arrangements for managing the needs of climate displaced people in their new communities need to be developed to account for issues related to impacts, livelihoods, community cohesion, and cultural diversity and values. Future research should address the significant gap in understanding the livelihoods of climate migrants in their cross border or international destination. More specifically, in developed countries where the employment sector is more formalized, there is less room for informal economic practices that are common in developing contexts. More formal employment arrangements make it challenging for migrants to establish new livelihoods, alongside other challenges such as language barriers, and other financial, social, cultural and well-being issues.

Limitations and future research scope

Limitations of this study.

There are some limitations to this systematic review; firstly, this review used ProQuest as the sole database for the analysis, and future work could extend the scope to include other major databases. Secondly, this study only considered English language literature, and there are likely to be significant publications in other languages relating to climate migration that were not included in this analysis. Thirdly, looking at pre-1990 or post-2019 literature could add more exciting findings to the search list, which would provide more informative literature. Finally, the outputs of this review are limited to the nature of the search terms, and thus, if other words or texts such as climate-induced relocation or mobility were used, it might extend the range of the review.

Toward a research agenda for climate migration

This review has highlighted several exciting future research opportunities that will build on the strong foundation of work over the past decades in the field of climate migration studies. These include the following research themes; (i) a richer understanding of the full range of impacts (such as social, economic, environmental, and cultural) of climate migration on host communities; (ii) in-depth analysis of the livelihoods of climate-induced migrants in their new destination; (iii) evidence-based research on internal and international climate migration with their sources; (iv) long-term migration policy development at national, regional, or international levels considering both climate migrants and host communities; (v) scope and application of geographic information systems and remote sensing in this area of research, and (vi) developing sustainable livelihood frameworks for climate migrants. The authors believe that academic contributions to these research themes will drive climate migration challenges toward long-term solutions, particularly in those countries that are going to be hosting increasing numbers of climate migrants in future.

This study aimed to understand the past three decades of academic endeavor on climate migration and to identify the gaps in the existing literature in order to inform a research agenda for future research. Climate change, climate-induced migration, and climate migrants are now considered significant global challenges. Climate migrants are identified as a vulnerable group, and a consideration of issues for this group is essential in addressing the goals of the SDGs and SFDRRR. There is a growing body of knowledge that reflects the global relevance of climate migration as a major current and future challenge (Boncour and Burson 2009 ). Addressing the issues and challenges of this form of migration will improve the survival and certain resettlement rights of climate migrants (Miller 2017 ). Therefore, this review contributes a research agenda for future climate migration studies. This study has revealed a critical need to establish a universally agreed definition of ‘climate-induced migrants’ and ‘climate-induced migration,’ which remains unclear to date. Lack of clarity only acts to reduce the visibility of issues related to climate-induced migration. In addition, there is a crucial need to improve the evidence base for climate-induced migration by improving current global datasets, to inform local, regional, and global policy development. Policies need to be future-looking in preparation for a rapid and significant increase in climate-related migration across the globe, within and across national borders. For instance, it is important for receiving countries to anticipate an upsurge in migration by developing appropriate policies to support new migrants, particularly regarding visa and immigration arrangements. Addressing current gaps in knowledge will lead to improved pathways to manage this global migration challenge, which is now a critical need if we are to achieve a sustainable future in a climate-challenged world.

Data availability

Data are available from the corresponding author upon reasonable request.

Abel G, Bijak J, Findlay A, Mccollum D, Winiowski A (2013) Forecasting environmental migration to the United Kingdom: an exploration using Bayesian models. Popul Environ 35(2):183–203. https://doi.org/10.1007/s11111-013-0186-8

Article   Google Scholar  

Apap J (2019) The concept of ‘climate refugee’: towards a possible definition. https://www.europarl.europa.eu/RegData/etudes/BRIE/2018/621893/EPRS_BRI(2018)621893_EN.pdf . Accessed 26 Aug 2021

Baird R, Migiro K, Nutt D, Kwatra A, Wilson S, Melby J, Pendleton A, Rodgers M, Davison J (2007) Human tide: the real migration crisis. https://www.christianaid.org.uk/sites/default/files/2017-08/human-tide-the-real-migration-crisis-may-2007.pdf . Accessed 11 Sep 2021

Bedford R, Bedford C, Corcoran J, Didham R (2016) Population change and migration in Kiribati and Tuvalu, 2015–2050: Hypothetical scenarios in a context of climate change. N Z Popul Rev 42:103–134

Google Scholar  

Berrang-Ford L, Ford J, Paterson J (2011) Are we adapting to climate change? Glob Environ Change 21(1):25–33. https://doi.org/10.1016/j.gloenvcha.2010.09.012

Black R (2001) Environmental refugees: myth or reality? In: UNHCR: New Issues in Refugee Research (No. 34). https://www.unhcr.org/research/working/3ae6a0d00/environmental-refugees-myth-reality-richard-black.html . Accessed 04 Sep 2021

Black R, Adger WN, Arnell NW, Dercon S, Geddes A, Thomas D (2011) The effect of environmental change on human migration. Glob Environ Change 21(SUPPL. 1):S3–S11. https://doi.org/10.1016/j.gloenvcha.2011.10.001

Boncour P, Burson B (2009) Climate change and migration in the South Pacific region: policy perspectives. Policy Q 5(4):13–20. https://doi.org/10.26686/pq.v5i4.4312

Bronen R (2008) Alaskan communities’ rights and resilience. Forced Migr Rev 31:30–32

Bronen R (2011) Climate-induced community relocations: creating an adaptive governance framework based in human rights doctrine. N Y Univ Rev Law Soc Change 35(2):357–407

Bronen R, Chapin FS (2013) Adaptive governance and institutional strategies for climate-induced community relocations in Alaska. Proc Natl Acad Sci USA 110(23):9320–9325. https://doi.org/10.1073/pnas.1210508110

Brown O (2008) Migration and climate change. In: IOM Migration Research Series (No. 31). https://publications.iom.int/books/mrs-no-31-migration-and-climate-change . Accessed 11 Sep 2021

Campbell JR (2014) Climate-change migration in the Pacific. Contemp Pac 26(1):1–28. https://doi.org/10.1353/cp.2014.0023

Chapagain B, Gentle P (2015) Withdrawing from agrarian livelihoods: environmental migration in Nepal. J Mt Sci 12(1):1–13. https://doi.org/10.1007/s11629-014-3017-1

Chen J, Mueller V (2018) Coastal climate change, soil salinity and human migration in Bangladesh. Nat Clim Change 8(11):981–985. https://doi.org/10.1038/s41558-018-0313-8

Comstock AR, Cook RA (2018) Climate change and migration along a Mississippian periphery: a fort ancient example. Am Antiq 83(1):91–108. https://doi.org/10.1017/aaq.2017.50

Connell J, Lutkehaus N (2017) Environmental refugees? A tale of two resettlement projects in coastal Papua New Guinea. Aust Geogr 48(1):79–95. https://doi.org/10.1080/00049182.2016.1267603

Coughlin J (2018) The Figure of the “Climate Refugee” in Inger Elisabeth Hansen’s Å resirkulere lengselen: avrenning foregår (2015). Scand Can Stud 25:68–90

de Haas H (2011) The determinants of international migration: conceptualising policy, origin and destination effects. IMI Working Pap Ser 32(2011):35

de Haas H (2021) A theory of migration: the aspirations-capabilities framework. Comp Migr Stud 9(1):1–35. https://doi.org/10.1186/S40878-020-00210-4

Dorent N (2011) Transitory cities: emergency architecture and the challenge of climate change. Development 54(3):345–351. https://doi.org/10.1057/dev.2011.60

Doyle EEH, Johnston DM, Smith R, Paton D (2019) Communicating model uncertainty for natural hazards: a qualitative systematic thematic review. Int J Disaster Risk Reduct 33:449–476. https://doi.org/10.1016/j.ijdrr.2018.10.023

Fussell E, Hunter LM, Gray CL (2014) Measuring the environmental dimensions of human migration: the demographer’s toolkit. Glob Environ Change 28(1):182–191. https://doi.org/10.1016/J.GLOENVCHA.2014.07.001

Gemenne F (2015) One good reason to speak of “climate refugees.” Forced Migr Rev 49:70–71

Hamza M, Koch I, Plewa M (2017) Disaster-induced displacement in the Caribbean and the Pacific. Forced Migr Rev 56:62–64

Held D (2016) Climate change, migration and the cosmopolitan dilemma. Global Pol 7(2):237–246. https://doi.org/10.1111/1758-5899.12309

Hingley R (2017) “Climate refugees”: an oceanic perspective. Asia Pac Policy Stud 4(1):158–165. https://doi.org/10.1002/app5.163

Huq ME, Sarker MNI, Prasad R, Hossain MA, Rahman MM, Al-Dughairi AA (2021) Resilience for disaster management: opportunities and challenges. In: Alam GMM, Erdiaw-Kwasie MO, Nagy GJ, Filho WL (eds) Climate vulnerability and resilience in the global south : human adaptations for sustainable futures, 1st edn. Springer, Cham, pp 425–442. https://doi.org/10.1007/978-3-030-77259-8_22

Chapter   Google Scholar  

IDMC (2017) Global Disaster Displacement Risk: A Baseline for Future Work. https://www.internal-displacement.org/publications/global-disaster-displacement-risk-a-baseline-for-future-work . Accessed 09 Sep 2021

IDMC (2019) Disaster displacement: a global review 2008–2018. https://environmentalmigration.iom.int/disaster-displacement-global-review-2008-2018 . Accessed 08 Sep 2021

IDMC (2021a) GRID 2021a: Internal displacement in a changing climate. Global Report on Internal Displacement, Internal Displacement Monitoring Centre. https://www.internal-displacement.org/global-report/grid2021/ . Accessed 14 June 2021

IDMC (2021b) IDMC Query Tool—Disaster. Global Internal Displacement Database. https://www.internal-displacement.org/database/displacement-data . Accessed 09 Dec 2021

IOM (2021) Environmental Migration: Recent Trends. Migration Data Portal, International Organization for Migration. https://migrationdataportal.org/themes/environmental_migration_and_statistics . Accessed 31 Aug 2021

Ionesco D, Mokhnacheva D, Gemenne F (2017) The atlas of environmental migration, 1st edn. Routledge, London. https://doi.org/10.4324/9781315777313

Book   Google Scholar  

IPCC (1990) IPCC First Assessment Report Overview. https://www.ipcc.ch/assessment-report/ar1/ . Accessed 10 Sep 2021

Islam MM, Sallu S, Hubacek K, Paavola J (2014) Migrating to tackle climate variability and change? Insights from coastal fishing communities in Bangladesh. Clim Change 124:733–746. https://doi.org/10.1007/s10584-014-1135-y

Jacobson C, Crevello S, Chea C, Jarihani B (2019) When is migration a maladaptive response to climate change? Reg Environ Change 19(1):101–112. https://doi.org/10.1007/s10113-018-1387-6

Kälin W, Cantor D (2017) The RCM Guide: a novel protection tool for cross-border disaster-induced displacement in the Americas. Forced Migr Rev 56:58–61

Kang MJ (2013) From original homeland to “permanent housing” and back: the post-disaster exodus and reconstruction of south Taiwan’s indigenous communities. Soc Sci Dir 2(4):85–105. https://doi.org/10.7563/SSD_02_04_08

King D, Bird D, Haynes K, Boon H, Cottrell A, Millar J, Okada T, Box P, Keogh D, Thomas M (2014) Voluntary relocation as an adaptation strategy to extreme weather events. Int J Disaster Risk Reduct 8:83–90. https://doi.org/10.1016/j.ijdrr.2014.02.006

Kniveton DR, Smith CD, Black R (2012) Emerging migration flows in a changing climate in dryland Africa. Nat Clim Change. https://doi.org/10.1038/nclimate1447

Laczko F, Aghazarm C (2009) Introduction and overview: enhancing the knowledge base. In: Laczko F, Aghazarm C (eds) Migration, environment and climate change: assessing the evidence. International Organization for Migration, Le Grand-Saconnex, pp 7–40

Locke JT (2009) Climate change-induced migration in the Pacific Region: sudden crisis and long-term developments. Geogr J 175(3):171–180. https://doi.org/10.1111/j.1475-4959.2009.00317.x

Mallett R, Hagen-Zanker J, Slater R, Duvendack M (2012) The benefits and challenges of using systematic reviews in international development research. J Dev Eff 4(3):445–455. https://doi.org/10.1080/19439342.2012.711342

Mallick B, Schanze J (2020) Trapped or voluntary? Non-migration despite climate risks. Sustainability 12(11):1–6. https://doi.org/10.3390/su12114718

Mallick B, Sultana Z (2017) Livelihood after relocation-evidences of Guchchagram project in Bangladesh. Soc Sci 6(3):1–19. https://doi.org/10.3390/socsci6030076

Marino E, Lazrus H (2015) Migration or forced displacement? The complex choices of climate change and disaster migrants in Shishmaref, Alaska and Nanumea, Tuvalu. Hum Organ 74(4):341–350. https://doi.org/10.17730/0018-7259-74.4.341

Maurel M, Tuccio M (2016) Climate instability, urbanisation and international migration. J Dev Stud 52(5):735–752. https://doi.org/10.1080/00220388.2015.1121240

Mayer B (2013) Environmental migration in the Asia-Pacific region: could we hang out sometime? Asian J Int Law 3(1):101–135. https://doi.org/10.1017/S204425131200029X

Mcleman R (2019) International migration and climate adaptation in an era of hardening borders. Nat Clim Change 9(12):911–918. https://doi.org/10.1038/s41558-019-0634-2

McLeman RA (2014) Climate and human migration: past experiences, future challenges. Cambridge University Press, Cambridge. https://doi.org/10.1017/CBO9781139136938

McLeman RA, Hunter LM (2010) Migration in the context of vulnerability and adaptation to climate change: insights from analogues. Wiley Interdiscip Rev Clim Change 1(3):450–461. https://doi.org/10.1002/wcc.51

Milán-García J, Caparrós-Martínez JL, Rueda-López N, de Pablo Valenciano J (2021) Climate change-induced migration: a bibliometric review. Glob Health 17(1):1–10. https://doi.org/10.1186/S12992-021-00722-3

Miller DS (2017) Climate refugees and the human cost of global climate change. Environ Justice 10(4):89–92. https://doi.org/10.1089/env.2017.29027.dm

Myers N (2002) Environmental refugees: a growing phenomenon of the 21st century. Philos Trans R Soc B Biol Sci 357(1420):609–613. https://doi.org/10.1098/rstb.2001.0953

Nagra S (2017) The Oslo principles and climate change displacement: missed opportunity or misplaced expectations? Carbon Clim Law Rev CCLR 11(2):120–135. https://doi.org/10.21552/cclr/2017/2/8

Nawrotzki RJ, Runfola DM, Hunter LM, Riosmena F (2016a) Domestic and International Climate Migration from Rural Mexico. Hum Ecol 44(6):687–699. https://doi.org/10.1007/s10745-016-9859-0

Nawrotzki RJ, Schlak AM, Kugler TA (2016b) Climate, migration, and the local food security context: introducing Terra Populus. Popul Environ 38(2):164–184. https://doi.org/10.1007/s11111-016-0260-0

Nishimura L (2015) ‘Climate change migrants’: impediments to a protection framework and the need to incorporate migration into climate change adaptation strategies. Int J Refug Law 27(1):107–134. https://doi.org/10.1093/ijrl/eev002

Obokata R, Veronis L, McLeman R (2014) Empirical research on international environmental migration: a systematic review. Popul Environ 36(1):111–135. https://doi.org/10.1007/s11111-014-0210-7

OHCHR (2018) The slow onset effects of climate change and human rights protection for cross-border migrants. https://www.ohchr.org/Documents/Issues/Migration/OHCHR_slow_onset_of_Climate_Change_EN.pdf . Accessed 10 Dec 2021

Olsson L (2015) Environmental migrants in international law: An assessment of protection gaps and solutions. Environmental Migration Portal: Climate Change, Displacement. https://environmentalmigration.iom.int/environmental-migrants-international-law-assessment-protection-gaps-and-solutions . Accessed 10 Dec 2021

Omeziri E, Gore C (2014) Temporary measures: Canadian refugee policy and environmental migration. Refuge 29(2):43–53. https://doi.org/10.25071/1920-7336.38166

Parrish R, Colbourn T, Lauriola P, Leonardi G, Hajat S, Zeka A (2020) A critical analysis of the drivers of human migration patterns in the presence of climate change: a new conceptual model. Int J Environ Res Public Health 17(17):1–20. https://doi.org/10.3390/ijerph17176036

Peel MC, Finlayson BL, Mcmahon TA (2007) Updated world map of the Köppen-Geiger climate classification. Hydrol Earth Syst Sci 11(5):1633–1644. https://doi.org/10.5194/hess-11-1633-2007

Perkiss S, Moerman L (2018) A dispute in the making. Account Audit Account J 31(1):166–192. https://doi.org/10.1108/AAAJ-06-2016-2582

Perumal N (2018) The place where I live is where I belong: community perspectives on climate change and climate-related migration in the Pacific island nation of Vanuatu. Island Stud J 13(1):45–64. https://doi.org/10.24043/isj.50

Petticrew M, Robert H (2006) Systematic reviews in the social sciences: a practical guide. Blackwell Publishing, Hoboken. https://doi.org/10.1002/9780470754887

Piguet E, Pécoud A, de Guchteneire P (2011) Migration and climate change: an overview. Refug Surv Q 30(3):1–23. https://doi.org/10.1093/rsq/hdr006

Piguet E, Kaenzig R, Guélat J (2018) The uneven geography of research on “environmental migration.” Popul Environ 39(4):357–383. https://doi.org/10.1007/s11111-018-0296-4

Poncelet A, Gemenne F, Martiniello M, Bousetta H (2010) A country made for disasters: environmental vulnerability and forced migration in Bangladesh. In: Afifi T, Jäger J (eds) Environment, forced migration and social vulnerability. Springer, Berlin, pp 211–222. https://doi.org/10.1007/978-3-642-12416-7

Prasain S (2018) Climate change adaptation measure on agricultural communities of Dhye in Upper Mustang, Nepal. Clim Change 148:279–291. https://doi.org/10.1007/s10584-018-2187-1

Pryce G, Chen Y (2011) Flood risk and the consequences for housing of a changing climate: an international perspective. Risk Manage 13(4):228–246. https://doi.org/10.1057/rm.2011.13

Rahaman MA, Rahman MM, Bahauddin KM, Khan S, Hassan S (2018) Health disorder of climate migrants in Khulna City: an urban slum perspective. Int Migr. https://doi.org/10.1111/imig.12460

Rahman MS, Gain A (2020) Adaptation to river bank erosion induced displacement in Koyra Upazila of Bangladesh. Prog Disaster Sci 5:1000552. https://doi.org/10.1016/j.pdisas.2019.100055

Rice JL, Burke BJ, Heynen N (2015) Knowing climate change, embodying climate praxis: experiential knowledge in Southern Appalachi. Ann Assoc Am Geogr 105(2):253–262. https://doi.org/10.1080/00045608.2014.985628

Scheffran J (2008) Climate change and security. Bull Atom Sci 64(2):19–25. https://doi.org/10.2968/064002007

Schwan S, Yu X (2017) Social protection as a strategy to address climate-induced migration. Int J Clim Change Strateg Manage 10(1):43–64. https://doi.org/10.1108/IJCCSM-01-2017-0019

Smith K, Smith K (2013) Environmental hazards: assessing risk and reducing disaster, 6th edn. Routledge, London. https://doi.org/10.4324/9780203805305

Tanyag M (2018) Resilience, female altruism, and bodily autonomy: disaster-induced displacement in Post-Haiyan Philippines. Signs J Women Cult Soc 43(3):563–585. https://doi.org/10.1086/695318

The World Bank (2018) Groundswell: preparing for internal climate migration. https://www.worldbank.org/en/news/infographic/2018/03/19/groundswell---preparing-for-internal-climate-migration . Accessed 29 June 2021

Warner K, Ehrhart C, de Sherbinin A, Adamo S, Chai-Onn T (2009) In search of shelter: mapping the effects of climate change on human migration and displacement. https://www.care.org/wp-content/uploads/2020/05/CC-2009-CARE_In_Search_of_Shelter.pdf . Accessed 11 Sept 2021

Weinthal E, Zawahri N, Sowers J (2015) Securitizing water, climate, and migration in Israel, Jordan, and Syria. Int Environ Agreem Polit Law Econ 15(3):293–307. https://doi.org/10.1007/s10784-015-9279-4

Werz M, Hoffman M (2016) Europe’s twenty-first century challenge: climate change, migration and security. Eur View 15(1):145–154. https://doi.org/10.1007/s12290-016-0385-7

White G (2012) Climate change and migration: security and borders in a warming world. Oxford University Press, Oxford. https://doi.org/10.1093/acprof:oso/9780199794829.001.0001

Wiegel H (2017) Refugees of rising seas. Science 357(6346):41. https://doi.org/10.1126/science.aan5667

Wilkinson E, Kirbyshire A, Mayhew L, Batra P, Milan A (2016) Climate-induced migration and displacement: closing the policy gap. https://www.odi.org/sites/odi.org.uk/files/resource-documents/10996.pdf . Accessed 12 March 2021

Ye Y, Fang X, Khan MAU (2012) Migration and reclamation in Northeast China in response to climatic disasters in North China over the past 300 years. Reg Environ Change 12(1):193–206. https://doi.org/10.1007/s10113-011-0245-6

Zaman ST (2021) Legal protection for the cross-border climate-induced population movement in south asia: exploring a durable solution. J Environ Law Litig 36:187–235

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The authors would like to thank Dr Douglas Hill, Dr Ashraful Alam and Dr Bishawjit Mallick for their feedback on the initial draft of this article.

This research has been supported by a University of Otago Doctoral Scholarship. Open Access funding is enabled and organized by CAUL and its Member Institutions.

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Ghosh, R.C., Orchiston, C. A systematic review of climate migration research: gaps in existing literature. SN Soc Sci 2 , 47 (2022). https://doi.org/10.1007/s43545-022-00341-8

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