New global migration estimates show rates steady since 1990, high return migration. Scientists have unveiled a new statistical method for estimating migration flows between countries. Using the so-called pseudo-Bayes approach, they show that rates of migration 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. Source 3k.