Why US immigration matters for the global advancement of science

While the impact of U.S. immigration on innovation in the U.S. has been well-studied, less attention has been paid to the relationship between U.S. immigration and global innovation. This paper fills this gap using novel data on a set of highly talented teenagers- participants in the International Mathematical Olympiad (IMO)-and presents three results. First, migrants to the U.S. are up to six times more productive than migrants to other countries, even after accounting for talent during one's teenage years. Second, most of the productivity differ-ence is associated with academics being more productive in the U.S. compared to those who stay home (with differences in entry rates into academia mattering less). Third, there is a large gap between aspirations to move to the U.S. and actual migration: about 2 in 3 of the world's most talented youth from developing countries would like to migrate to the U.S. for their undergraduate studies, but only 1 in 4 do, with financing constraints being a key barrier. A back of the envelope calculation suggests that removing constraints on immigration could increase the global scientific output of future cohorts by up to 50 %.