Optimal Fiscal and Monetary Policy with Occasionally Binding Zero Bound Constraints

During the Great Recession, the government provided large fiscal stimulus in an economic environment characterized by a high degree of uncertainty on the future course of the economy while the nominal interest rate was constrained at the zero lower bound. While many papers have analyzed the effects of fiscal policy at the zero lower bound, they all do so in a deterministic environment. This paper studies optimal government spending and monetary policy when the nominal interest rate is subject to the zero lower bound constraint in a stochastic environment. In the presence of uncertainty, the government chooses to increase its spending when at the zero lower bound by a substantially larger amount than it would in the deterministic environment. The welfare effect of fiscal policy is nuanced in the stochastic environment if the government cannot commit. Although the access to government spending policy increases welfare in the face of a large deflationary shock, it can decrease welfare during normal times as the government reduces the nominal interest rate less aggressively before reaching the zero lower bound.