Robust Monetary Policy Under Uncertainty About the Lower Bound

Central banks face uncertainty about the true location of the effective lower bound (ELB) on nominal interest rates. We model optimal discretionary monetary policy during a liquidity trap when the central bank designs policy that is robust with respect to the location of the ELB. If the central bank fears the worst-case location of the ELB, monetary conditions will be more expansionary in the period before the liquidity trap.