The Downside of Good Peers: How Classroom Composition Differentially Affects Men’s and Women’s STEM Persistence

This paper investigates whether class composition can help explain why women are disproportionately more likely to fall out of the “STEM†pipeline. Identification comes from a standardized enrollment process at a large public university that essentially randomly assigns freshmen to different mandatory introductory chemistry lectures. Using administrative data, I find that women who are enrolled in a class with higher ability peers are less likely to graduate with a STEM degree, while men’s STEM persistence is unaffected. The effect is largest for women in the bottom third of the ability distribution. I rule out that this is driven solely by grades.