Optimal Monetary Policy in a Liquidity Trap
We consider the consequences for monetary policy of the zero floor for nominal interest rates. The zero bound can be a significant constraint on the ability of a central bank to combat deflation. We show, in the context of an intertemporal equilibrium model, that open-market operations, even of unconventional' types, are ineffective if they do not change expectations about the future conduct of policy; in this sense, a liquidity trap' is possible. Nonetheless, a credible commitment to the right sort of history-dependent policy can largely mitigate the distortions created by the zero bound. In our model, optimal policy involves a commitment to adjust interest rates so as to achieve a time-varying price-level target, when this is consistent with the zero bound. We also discuss ways in which other central-bank actions, while irrelevant apart from their effects on expectations, may help to make credible a central bank's commitment to its target, and consider implications for the policy options currently available for overcoming deflation in Japan.
Eggertsson, Gauti B. and Michael Woodford. "The Zero Bound On Interest Rates And Optimal Monetary Policy," Brookings Papers on Economic Activity 34, 2003-1 (2003): 139-235.