Title: From Shocks to Waves
Description: What causes democratic waves? This dissertation argues that sudden shifts in the distribution of power among major states can help explain the wave-like spread of democracy over the past century. These hegemonic shocks lead to bursts of regime change by creating unique incentives and opportunities for domestic reforms, and do so through three sets of mechanisms - hegemonic coercion, influence, and emulation. Namely, shocks produce windows of opportunity for external regime imposition, enable rising great powers to expand networks of trade and patronage, and inspire imitators by credibly revealing hidden information about regime effectiveness to foreign audiences. I find strong statistical support for the idea that shifts in hegemonic power have shaped waves of democracy, fascism, and communism in the twentieth century. The statistical analysis is supplemented by case studies of three hegemonic shocks: World War I, the Great Depression, and World War II. Departing from theories that focus on the internal determinants of domestic reforms, this dissertation argues that regime success in the twentieth century is deeply tied to rapid changes in the global distribution of power, a relationship often obscured by the vivid particularities of local transformations.