This paper revisits the political economy of transitions to democracy. We build on a canonical rational choice model of democratization by introducing demography, arguing that the demographic structure of a society shapes the material incentives for a democratic movement. A population’s youth cohort can benefit from democratic improvements over a longer time horizon and may have a lower opportunity cost of participatingin democratic movements than older cohorts. Hence, a rise in the population’s proportion of youth during the demographic transition opens a democratic “windowof opportunity” as the heightened incentives for a democratic movement might prompt an autocratic elite to concede more democracy. We test this prediction on two long country-year panel data sets containing detailed demographic data. Fixed-effects panel regressions demonstrate that an increase in the youth ratio is robustly associated with democratic improvements.The effect is particularly pronounced for “youth bulges” measured as the proportion of the population between the ages of 15 and 19. Two distinct instrumental variable strategies, using (i) lagged fertility rates in neighboring countries and (ii) past climatic conditions, allow for a causal interpretation of this correlation. Furthermore, the positive impact of the youth ratio on democratic improvements is more pronounced during recessions suggesting that demographic and macro-economic cycles are complementary channels. Finally, we show that low intensity conflict, such as riots, might act as a transmission channel, facilitating thepositive impact of a high youth ratio on the probability of a democratic improvement.