The Sustainability of Budget Deficits in a Stochastic Economy (Revision of 6-90) (Reprint 014)

The paper studies the sustainability of government budget deficits in a stochastic economy. The general equilibrium setting permits a rigorous derivation of the relevant transversality conditions and intertemporal budget constraints. The transversality condition on government debt requires a zero limit of discounted future government debt, where the discount rate depends on the probability distribution of future debt over states of nature. The government’s intertemporal budget constraint requires that the discounted present value of primary surpluses matches initial debt, where the discount rate on future government spending and taxes depends again on the probability distribution of these variables over states of nature. Contrary to assertions made in the literature, the discount rates on future government debt, spending, and taxes are generally not related to the rates of return on government debt. Most importantly, future government debt in the transversality condition cannot be discounted at the safe interest rate, not even if government debt is safe. Debt discounted at the safe interest rate may well diverge to infinity under sustainable policies. This result raises questions about some recent empirical papers testing the sustainability of U.S. fiscal policy. In addition, the paper shows that the average level of primary deficits provides little evidence on sustainability. Policies with permanent expected primary deficits can be sustainable, in particular when the safe interest rate is below the average growth rate of the economy.