Whereas some view the macroeconomy as overall stable and on a smooth long-run growth path, others argue it is unstable with repeated periods of booms and busts. This column suggests that the market economy is inherently unstable and booms and busts arise endogenously as the results of market incentives. Monetary policy is then perhaps not the right tool for addressing macroeconomic fluctuations. Instead, policies aimed at changing the incentives would be more appropriate.