Testing monetary policy optimality using volatility outcomes: a novel approach

We propose a method to assess the efficiency of macroeconomic outcomes using the restrictions implied by optimal policy DSGE models for the volatility of observable variables. The method exploits the variation in the model parameters, rather than random deviations from the optimal policy. In the new Keynesian business cycle model this approach shows that optimal monetary policy imposes tighter restrictions on the behavior of the economy than is readily apparent. The method suggests that for the historical output, inflation and interest rate volatility in the United States over the 1984-2005 period to be generated by any optimal monetary policy with a high probability, the observed interest rate time series should have a 25% larger variance than in the data.