MigrationGlobal migration rates steady since 1990, high return migration
On today’s increasingly crowded globe, human migration can strain infrastructure and resources. Accurate data on migration flows could help governments plan for and respond to immigrants. Yet these figures, when available, tend to be spotty and error-ridden, even in the developed world. Researchers have developed approaches to estimate migration rates, but even the best of these rely on unrealistic assumptions about the mass movement of people and yield migration rates that can fall far below reality.
On today’s increasingly crowded globe, human migration can strain infrastructure and resources. Accurate data on migration flows could help governments plan for and respond to immigrants. Yet these figures, when available, tend to be spotty and error-ridden, even in the developed world. Researchers have developed approaches to estimate migration rates, but even the best of these rely on unrealistic assumptions about the mass movement of people and yield migration rates that can fall far below reality.
In a paper published online in the Proceedings of the National Academy of Sciences, two scientists at the University of Washington unveiled a new statistical method for estimating migration flows between countries, using the so-called pseudo-Bayes approach. They show that rates of migration — defined as an international move followed by a stay of at least one year — are higher than previously thought, but also relatively stable, fluctuating between 1.1 and 1.3 percent of global population from 1990 to 2015. In addition, since 1990 approximately 45 percent of migrants have returned to their home countries, a much higher estimate than other methods.
These more accurate estimates of migration will ultimately help both migrants and the people who assist them, said senior author Adrian Raftery, a UW professor of statistics and sociology.
“Planning for migration is no simple task,” said Raftery. “You need everything from medical infrastructure and trained personnel to elementary schools — and governments rely on accurate demographic estimates to help them put the right plans and responses into place.”
Countries collect migration data through immigration forms at ports of entry, but answers on these forms may contain mistakes, and often fail to collect the types of comprehensive information that demographers need to measure migration accurately. Census forms also tend to ask people where they were born, but usually not when they moved, information which does not accurately reflect the true level of movement.
“Migration is much more than the place you left and the place you ultimately settled in,” said Raftery. “Researchers have tried for years to develop statistical methods that capture the comprehensive picture of human migration across the globe.”
