A general theory (and some evidence) of expectation traps in monetary policy

I show that multiple equilibria are a general property of economies under full monetary policy discretion. Three simple conditions are sufficient to rule out, generically, a unique equilibrium in a static economy. The key departure from Barro and Gordon (1983) is to consider bounded welfare costs of inflation. I also show that in a two Markov equilibrium economy the inflation response to certain perturbations is, generically, qualitatively different in each equilibrium. Finally, I discuss some evidence on inflation dynamics that supports the hypothesis that U.S. monetary policy was caught in an expectation trap during the high inflation episode of the 1970s.