SAN FRANCISCO, Dec. 24 (Xinhua) -- U.S. scientists from the University of Washington (UW) have come up with a greater accuracy in estimating global migration rate by applying a new statistical approach that corrects past errors and inaccuracies, a study showed Monday.
Two UW researchers found that the rates of global migration between countries are higher than previously estimated but relatively stable, fluctuating between 1.1 percent and 1.3 percent of global population from 1990 to 2015.
Previous data of global migrant population were often full of errors, patchy and incomplete, because they mostly came from "unrealistic assumptions about the mass movement of people and yield migration rates that can fall far below reality," said the study published Monday in the Proceedings of the National Academy of Sciences.
Two UW scientists, Adrian Raftery and Jonathan Azose, unveiled in their paper a new statistical method for estimating worldwide migration flows, called pseudo-Bayes approach, which can better measure the rate of flows of people between countries.
By adopting the new statistical approach, they found that about 45 percent of migrants have returned to their home countries since 1990, a much higher estimate than other methods.
They incorporated elements of other statistical methods in the pseudo-Bayes approach and calibrated their estimates against a relatively reliable model of migration among 31 European countries.
They found that the results obtained by the pseudo-Bayes method were accurate to within a factor of three, better than many existing estimates.
Their estimates supported by the pseudo-Bayes approach showed that about 67 million to 87 million migrants were recorded over each five-year period from 1990 to 2015.
Although the total number of migrants rose from 1990 to 2015, the migration rate over that period remained within a relatively stable range of 1.1 percent and 1.3 percent.
According the study of the UW scientists, more than 60 percent of migration was emigration during the 25 years, and transition migration were well below 9 percent, with the return migration rate accounting for 26 percent to 31 percent, more than twice that of other migration estimates.
"Our estimate shows a higher global flow of migrants in large part because it indicates that return migration is much higher than previously thought," said Azose, the paper's lead author.
"Migration is much more than the place you left and the place you ultimately settled in," said Raftery, the study's senior author.
More accurate estimates of migration will ultimately help both migrants and the people who assist them, such as governments that rely on accurate demographic estimates to help them put in place the right plans and response mechanisms.