The rapidly growing federal government debt has become a concern for policy makers and the public. Yet the U.S. government has seemingly unbounded access to credit at low interest rates. Historically, Treasury yields have been below the growth rate of the economy. The paper examines the ramifications of debt financing at low interest rates. Given the short maturity of U.S. public debt – over $2.5 trillion maturing in 2010 – investor expectations are critical. Excessive debts justify reasonable doubts about solvency and monetary stability and thus undermine a financing strategy built on the perception that U.S. debt is safe.

This paper examines the impact of government policy on the allocation of aggregate risks in a stochastic OG model with production. The market allocation of risk depends significantly on the young generation’s willingness to substitute intertemporally and on government policy. Safe government debt shifts productivity risk from old to young while wage-indexed social security is essentially neutral. I also compare the market allocation to the efficient allocation of risk. The market allocation is generally inefficient, except for the special case of wage-proportional incomes and logarithmic utility. Safe government debt seems to shift risk in the wrong direction.

Aging societies will have to rely increasingly on private savings to finance retirement. The natural savings vehicles, stocks and bonds, are unfortunately lacking key risk-sharing features that are built into public retirement. Innovative government debt management can address this problem. The optimal policy supplies retirees with securities that share the financial risks of aggregate productivity, asset valuation, and demographic shocks across generations. As the population ages, state-contingent government bonds are a better risk sharing tools than pensions, which become too costly, or taxation, which raises time-consistency problems. Wage-indexed and longevity-indexed bonds in particular yield unambiguous efficiency improvements. To the extent that public pensions remain important, plans with wage-indexed defined benefits seem preferable to defined contributions or price-indexed plans. Capital income taxes and pension trust funds can play a supporting role for risk sharing.

The paper examines alternative options for managing public debt and public assets in a government balance sheet framework that includes the Treasury, the Federal Reserve, and social security. Even after September 11, U.S. fiscal policy is on a trajectory to accumulate substantial “uncommitted funds.” The paper examines how such funds should be invested. I conclude that high-quality fixed-income securities are the best benchmark and that social security is the most appropriate government asset manager. The analysis of policy alternatives reveals a trilemma between maintaining a liquid Treasury market, minimizing rent-seeking, and facilitating intergenerational risk sharing.

Most state and local retirement plans strive for full funding, at least by actuarial standards. Funding measured at market values fluctuates and often falls short. A common argument for full funding is that pensions are a form of deferred compensation that does not justify a debt. The paper examines public finance, political economy, and financial market issues that bear on optimal funding, broadly and in a series of models. In a model where most taxpayers hold debt and face intermediation costs, returns on pension assets are less than taxpayers’ cost of borrowing. Pension funding is costly and hence zero funding is optimal. The model also implies that unfunded pension promises are properly discounted at a rate strictly greater than the government’s borrowing rate. If pension funds serve as collateral, funding can be warranted despite the cost. This is shown in a model with legal ambiguity and default risk. Except in special cases, the optimal funding ratio is less than full funding.

We calculate the harm a birth imposes on others when greenhouse gas emissions are a problem and a cap limits emissions damage. This negative population externality, which equals the corrective Pigovian tax on having a child, is substantial in calibrations. In our base case, the Pigovian tax is 21 percent of a parent's lifetime income in steady state and 5 percent of lifetime income immediately after imposition of a cap, per child. The optimal population in steady state, which maximizes utility taking account of the externality, is about one quarter of the population households would choose voluntarily