New Keynesian versus old Keynesian government spending multipliers

Renewed interest in fiscal policy has increased the use of quantitative models to evaluate policy. Because of modelling uncertainty, it is essential that policy evaluations be robust to alternative assumptions. We find that models currently being used in practice to evaluate fiscal policy stimulus proposals are not robust. Government spending multipliers in an alternative empirically estimated and widely cited new Keynesian model are much smaller than in these old Keynesian models; the estimated stimulus is extremely small with GDP and employment effects only one-sixth as large and with private sector employment impacts likely to be even smaller. We investigate the sensitivity of our findings with regard to the response of monetary policy, the zero bound on nominal interest rates and the inclusion of an empirically relevant degree of rule-of-thumb behaviour in the new Keynesian model. In addition, we relate our findings using estimated structural macroeconomic models to the recent literature using reduced-form regression techniques.