Scholars continue to disagree about the relationship between economic development and democracy. I review the history of the debate and summarize patterns visible in data available today. I find a strong and consistent relationship between higher income and both democratization and democratic survival in the medium term (10–20 years), but not necessarily in shorter time windows. Building on several recent studies, I sketch out a new conditional modernization theory, which can account for such lags. The key idea is that the effect of development on democracy is triggered by disruptive events such as economic crises, military defeats, or—most generally—leader change. Political outcomes depend on both the development level and, at intermediate income ranges, how citizens coordinate. Waves of leader turnover in autocracies correlate with temporarily stronger links between income and democratization, which, in turn, coincide with the first two waves of democracy.