Fiscal multipliers under an interest rate peg of deterministic vs. stochastic duration

This paper revisits the size of the fiscal multiplier. The experiment is a fiscal expansion under the assumption of a pegged nominal rate of interest. We demonstrate that a quantitatively important issue is the articulation of the exit from the policy experiment. If the monetary-fiscal expansion is stochastic with a mean duration of T periods, the fiscal multiplier can be unboundedly large. However, if the monetary-fiscal expansion is for a fixed T periods, the multiplier is much smaller. Our explanation rests on a Jensen’s inequality type argument: the deterministic multiplier is convex in duration, and the stochastic multiplier is a weighted average of the deterministic multipliers. The quantitative difference in the two multipliers also arises in a model with capital, and in the baseline nonlinear model. However, the differences between the two is less pronounced in the nonlinear models.