Over the past four decades, the earnings gap between college graduates and non-graduates has widened substantially, prompting interest in policies aimed at promoting higher education among low-income students.

Over the past four decades, the earnings gap between college graduates and non-graduates has widened substantially, prompting interest in policies aimed at promoting higher education among low-income students. A key challenge for these policies is the high college dropout rate. This paper develops a dynamic model of college enrollment and completion with rich individual heterogeneity to assess how various factors influence college attendance, dropout, and graduation. We estimate the model using data from longitudinal surveys, results of quasi-experimental studies on grant aid, and large-scale randomized controlled trials. We use the model to simulate the effects of tuition subsidies, college loans, financial incentives, and increased pre-college skills on attendance and completion. We find moderate effects of most unconditional financial policies on attendance, with small effects on completion conditional on attendance. By contrast, some merit-based incentives, such as forgiving student loans upon receipt of a bachelor’s degree, have substantial effects. However, this type of policy and other financial subsidies accrue even more than the others to students from relatively wealthy backgrounds. Overall, it appears infeasible to design a financial aid policy that is simultaneously effective in raising attainment and fiscally progressive. By comparison, we find that the greatest potential for increasing attainment could come from better preparing students for college. We thank Zach Bleemer, Dereck Neal, Mike Lovenheim, Philipp Kircher, and seminar/conference participants at a number of places for their helpful feedback. All errors are ours. The views expressed herein are those of the authors and do not necessarily reflect the views of the National Bureau of Economic Research. In addition toworking papers, the NBER disseminates affiliates’ latest findings through a range of free periodicals—theNBER Reporter, theNBER Digest, theBulletin on Health, theBulletin on the Economics of Alzheimer's, and theBulletin on Entrepreneurship—as well asresearch spotlights, lectures, and panel videos.