Optimal Fiscal Policy in a Model with Uninsurable Idiosyncratic Income Risk

Abstract We study optimal fiscal policy in a standard incomplete-markets model with uninsurable idiosyncratic income risk, where a Ramsey planner chooses time-varying paths of proportional capital and labour income taxes, lump-sum transfers (or taxes), and government debt. We find that (1) short-run capital income taxes are effective in providing redistribution since the tax base is relatively unequal and inelastic; (2) an increasing pattern of labour income taxes over time mitigates intertemporal distortions from capital income taxes; (3) the optimal policy increases overall transfers, calibrated initially to the US welfare system, by roughly 50\%; (4) two-thirds of the welfare gains come from redistribution and the remaining third come mostly from insurance; and (5) redistribution also leads to a more efficient allocation of labour via wealth effects on labour supply—lower productivity households can afford to work relatively less.