With nearly 200 million people in the world living outside their country of birth, international migration patterns are a matter of great interest to planners and policymakers around the world. 

Although the causes of international migration are varied and complex, persistent economic disparities between the areas of origin and destination have been at the root of most migration flows in the past half century.  Due to low fertility in many major industrialized countries and much higher fertility rates in many developing nations, international migration of workers is expected to increase, but by how much?  Oil rich countries in the Persian Gulf have been attracting large numbers of workers from South Asia and other countries in the Middle East, but will this trend persist?  Will India and China, despite their growing economies, continue to export workers?  We may be getting closer to some answers.

Four researchers, led by Joel Cohen at Rockefeller University and Marta Roig of the United Nation’s Population Division, have developed a statistical model for predicting international migration patterns.  The new model, published this week in the online early edition of the Proceedings of the National Academy of Sciences, analyzed 43,653 reports from 11 counties of migration from 1960-2004.

Cohen, the chief author of the study, is quoted in news reports as saying, “From year to year, it has been difficult to calculate how the world's population ebbs and flows between countries other than guessing that this year will resemble last year. But that is critical information in so many ways, and this model offers a new and unified approach that, we hope, will be of global benefit.”

So how accurate is the new model?  Cohen says "Our model accounts for roughly 60 percent of the variation in annual numbers of migrants from any country or region to any other, based on historical data, and nothing has come close to this.”

Cohen emphasized in the article that, "This is only a first step, but it is a step that had not been made before. I hope this stimulates countries to come together and improve the standards by which they collect migration data. The data available to us are incomplete, inconsistent and in some cases contradictory. Better data in the future will help to improve models like this."

An abstract of the new study is available on-line on the NAS website.  A copy of the full study can be downloaded for a fee.   For more background on international migration, see our earlier (2003) executive summary.