July 2023, Paper: "Economics is among the most popular undergraduate majors. However, even at the best research universities and liberal arts colleges men outnumber women by two to one, and overall there are about 2.5 males to every female economics major. The Undergraduate Women in Economics (UWE) Challenge was begun in 2015 for one year as a randomized controlled trial with 20 treatment and 68 control schools to evaluate the impact of light-touch interventions to recruit and retain female economics majors. Treatment schools received funding, guidance, and access to networking with other treatment schools to implement programs such as providing better information about the application of economics, exposing students to role models, and updating course content and pedagogy. Using 2001-2021 data from the Integrated Postsecondary Education Data System (IPEDS) on graduating BAs, we find that UWE was effective in increasing the fraction of female BAs who majored in economics relative to men in liberal arts colleges. Large universities did not show an impact of the treatment, although those that implemented their own RCTs showed moderate success in encouraging more women to major in economics. We speculate on the reasons for differential treatment impact."