Abstract
We exploit an institutional reduction in the costs of acquiring advanced high school mathematics to assess the causes and consequences of fewer girls choosing advanced mathematics. Girls at the top and boys at the middle of the mathematics ability distribution took more mathematics because of the cost reduction. We estimate a positive average earnings effect encompassing girls completing more advanced and more mathematics intensive college degrees, choosing more competitive careers and climbing higher up the corporate hierarchy. Encouraging more students to opt for advanced mathematics has a sizeable positive earnings effect for girls, but no effect for boys at the margin.