Nolan McCarty, Susan Dod Brown Professor of Politics and Public Affairs and Chair, Department of Politics describes how income inequality and political polarization have both increased dramatically in the United States over the last several decades. Research suggests that these two phenomena may be related and mutually reinforcing, and in this lecture, Professor McCarty presents credible causal estimates of the effect of income inequality on polarization within states. Presented as the 2015 Fall Football Lecture.