Liquidity Trap and Optimal Monetary Policy Revisited

This paper investigates history dependent easing known as a conventional wis- dom of optimal monetary policy in a liquidity trap. We show that, in an economy where the rate of inflation exhibits intrinsic persistence, monetary tightening is earlier as inflation becomes more persistent. This property is referred as early tightening and in the case of a higher degree of inflation persistence, a central bank implements front-loaded tightening so that it terminates the zero interest rate policy even before the natural rate of interest turns positive. As a prominent feature in a liquidity trap, a forward guidance of smoothing the change in inflation rates contributes to an early termination of the zero interest rate policy.