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Feldstein, Martin

This paper examines the risk aspects of an investment-based defined contribution Social Security plan. We focus on the risk after the plan is fully phased in. Individuals deposit a fraction of wages to a Personal Retirement Account (PRA), invest these funds in a 60:40 equity-debt mix, and in a similarly invested annuity at age 67. The value of the assets follows a random walk with mean and variance of a 60:40 equity-debt portfolio over the period 1946-95, a mean log return of 5.5 percent (net of administrative costs of 0.4 percent) and a standard deviation of 12.5 percent. We study he stochastic distributions of this process by doing 10,000 simulations of the 80-year experience of the cohort that reached age 21 in 1998. The resulting annuities are compared to the future defined benefits specified in current law (the benchmark' benefits). With no uncertainty, a 5.5 percent log return would permit the benchmark benefits to be purchased with PRA deposits of 3.1 percent of payroll, only one-sixth of the pay-as-you-go tax needed for the benchmark benefits. Saving a higher share of wages provides a cushion' that protects the individual from the risk of an unacceptably low level of benefits. For example, PRA deposits of 6 percent of wages reduces the probability that the benefits are less than the benchmark to 0.17 and the probability that they are less than 61 percent of the benchmark to 0.05. PRA deposits of 9 percent of wages (half of the tax rate required in a pay-as-you-go system) would substantially reduce these risks. This pure investment-based plan is an extreme case. The investment risk can be reduced further by using a mixed system that combines pay-as-you-go and investment-based components or that makes intergenerational transfers conditional on the performance of stock and bond prices.

This paper shows how a new type of derivative product that could be provided by private financial markets could in principle be used to guarantee that an investment-based Social Security reform provides at least the level of real retirement income that is projected in current Social Security rules. In effect, future retirees could purchase a put option' that guarantees that the future retirement benefit will not fall below the level projected in current Social Security law or some other chosen level. To pay for this guarantee, they would agree to give up the part of the annuity payments which exceeds a given level, effectively selling a call option on the stream of payments. This market-based approach could be completely voluntary, leaving each individual to decide what level of guarantee he wants. The higher the minimum guarantee that the individual chooses, the more of the potentially higher returns he must give up. The financial market can thus tailor each individual's product to his own risk preferences. Alternatively, the government might require that any product that is sold as part of the investment-based Social Security reform must include at least some such market-based guarantee. Our analysis calculates some of the tradeoffs that could be provided in today's financial markets. We show that it is feasible to protect future benefits equal to those projected in current law with a combination of the current payroll tax rate and Personal Retirement Account savings equal to 2.5 percent of covered earnings. Raising the savings rate to 3.0 percent increases substantially the amount of the return that the individual can keep, raising it to 145 percent of the currently projected level of benefits. Reducing the guarantee level to 90 percent of the projected future benefits would increase this upside potential to 150 percent of the currently projected level of benefits with a 2.5 percent saving rate and 195 percent of the currently projected benefits with a 3.0 percent saving rate.