This paper examines the implications of uncertainty about the effects of monetary policy for optimal monetary policy with an application to the current situation. Using a stylized macroeconomic model, I derive optimal policies under uncertainty for both conventional and unconventional monetary policies. According to an estimated version of this model, the U.S. economy is currently suffering from a large and persistent adverse demand shock. Optimal monetary policy absent uncertainty would quickly restore real GDP close to its potential level and allow the inflation rate to rise temporarily above the longer-run target. By contrast, the optimal policy under uncertainty is more muted in its response. As a result, output and inflation return to target levels only gradually. This analysis highlights three important insights for monetary policy under uncertainty. First, even in the presence of considerable uncertainty about the effects of monetary policy, the optimal policy nevertheless responds strongly to shocks: uncertainty does not imply inaction. Second, one cannot simply look at point forecasts and judge whether policy is optimal. Indeed, once one recognizes uncertainty, some moderation in monetary policy may well be optimal. Third, in the context of multiple policy instruments, the optimal strategy is to rely on the instrument associated with the least uncertainty and use alternative, more uncertain instruments only when the least uncertain instrument is employed to its fullest extent possible.
C. Williams, John. 2013. “A Defense of Moderation in Monetary Policy,” Federal Reserve Bank of San Francisco Working Paper 2013-15. Available at https://doi.org/10.24148/wp2013-15