RT Journal Article SR Electronic T1 Dynamics of the Gender Gap in High Math Achievement JF Journal of Human Resources JO J Hum Resour FD University of Wisconsin Press SP 0620-10972R1 DO 10.3368/jhr.58.5.0620-10972R1 A1 Glenn Ellison A1 Ashley Swanson YR 2021 UL http://jhr.uwpress.org/content/early/2021/08/04/jhr.58.5.0620-10972R1.abstract AB We examine dynamics in the gender gap in high school mathematics achievement using competition data. A clear gender gap is present by 9th grade, and the gap widens over time. Gender-related differences in dropout rates and in the mean and variance of year-to-year improvement contribute to the widening of the gender gap. The most important difference is that fewer girls make large enough gains to improve their rankings. We also document a discouragement effect: among students falling just short of qualifying for a prestigious second-stage exam, some drop out of future years, and this reaction may be stronger among girls.