Estimating global migration flows over the past decades
A new indirect estimation methodology, developed and applied by IIASA researchers, has quantified trends in global international migration flows over the past 55 years for the first time. These estimates provide a more comprehensive picture of past migration patterns than currently available figures in reported flow data produced by individual countries, or migrant stock data that do not capture the dynamic nature of movements over time.
Global international migration is an ever-changing process. Migrant stock data commonly used for the analysis of migration patterns, only capture part of the dynamic nature of international migration. An indirect estimation methodology, developed and applied by IIASA researchers, produces bilateral migration flow estimates that are demographically consistent with past population totals, births and deaths, and hence provides a more robust basis for understanding contemporary migration patterns where no comprehensive source of global migration flow data exists .
In their study, the researchers derived estimates of international migration flows by gender, between all countries, for five-year periods between 1960 and 2015. They found that, while estimated global migration flows generally increase over time, the percentage of the global population that migrates remains fairly steady at 0.65 of the global population over each five year period. This result supports similar findings in the migration literature on the lack of empirical evidence for the acceleration in global international migration, and suggests a shift in the directions of flows linked to major geopolitical and economic movements.
The bilateral estimates produced in this study quantify trends in global international migration flows over the past 55 years for the first time. Traditional migration receiving countries such as Australia, Canada, New Zealand, and the USA, for example, have seen continuously increasing numbers of migrants arriving. More recent growth is evident into countries in Northern-, Southern-, and Western Europe, while a growing number of migration flows were estimated along migrant corridors between countries in South Asia (such as Bangladesh, India, and Pakistan) to West Asia (such as Qatar, Saudi Arabia, and the United Arab Emirates), and from Asia to North America. In addition, large migrant transitions were also estimated in selected periods within Africa or Eastern Europe during times of armed conflict or political change.
The estimates produced can potentially be used as inputs into global population projection models. International projection-making agencies commonly use simplistic assumptions of net-migration measures derived as residuals from demographic accounting. However, past net migration can often be volatile and introduce bias when projecting populations . The bilateral migration estimates produced in this research however, allow for more detailed scenarios to be formulated based on changes in migration patterns related to changing future push and pull factors in origin and destination countries, and corridor specific factors related to linkages between countries or groups of countries.
 Abel G (2017). Estimates of Global Bilateral Migration Flows by Gender between 1960 and 2015. International Migration Review: 1-44. Rogers A (1990). Requiem for the Net Migrant. Geographical Analysis 22(4): 283–300.
- Asian Demographic Research Institute (ADRI), China
Top image © blvdone | Shutterstock