Comparative advantage and gender gap in STEM

Why are females, compared with males, both more likely to have strong STEM-related performance and less likely to enter a STEM field later on? We exploit random classroom assignment to identify the impact of comparative STEM advantage on specialization decisions. Comparative STEM advantage is proxied by the within-classroom ranking of the ratio of STEM over non-STEM performance. We find that females with a higher comparative STEM advantage are more likely to choose a STEM school track and apply for a STEM degree. Comparative STEM advantage explains 12 percent of the underrepresentation of qualified females in the earliest instance of STEM specialization.