Why does stock volatility increase when output declines? The theory of investment under uncertainty implies that political uncertainty may simultaneously increase volatility and reduce output. Though cause and effect are typically hard to separate, the transition from Imperial to Weimar Germany offers a natural experiment because major political events left clear traces on stock prices. Current and past increases in volatility are associated with output declines, consistent with U.S. experience. However, political events are more clearly the source of volatility, and the results support the view that the relationship between volatility and output reflects the joint effects of political factors.