Welfare-improving Consumption Tax in the Presence of Wage Tax under Idiosyncratic Returns from Investment and Incomplete Markets

In a standard multi-period model, consumption tax and wage tax are equivalent. I show that when a capital market is incomplete---in the sense that the rates of return from risky investments are idiosyncratic and there is no insurance for such idiosyncratic risk---the introduction of consumption tax in the presence of wage tax improves welfare. This holds true even in the presence of optimal or non-optimal capital income taxes. In the general equilibrium model, the optimal level of consumption tax is determined to balance the benefits of the risk-sharing effect and asset accumulation effect and the costs of postponing government revenue to later periods.