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Social Security Money's Worth


John Geanakoplos


Yale University - Cowles Foundation

Olivia S. Mitchell


University of Pennsylvania - The Wharton School; National Bureau of Economic Research (NBER)

Stephen P. Zeldes


Columbia Business School - Finance and Economics; National Bureau of Economic Research (NBER)

August 1998

Columbia Business School, PaineWebber Working Paper No. PW-98-05

Abstract:     
This paper describes how three money's worth measures--the benefit-to-tax ratio, the internal rate of return, and the net present value--are calculated and used in analyses of social security reforms, including systems with privately managed individual accounts invested in equities. Declining returns from the U.S. social security system prove to be the inevitable result of having instituted an unfunded (pay-as-you-go) retirement system that delivered $7.9 trillion of net transfers (in 1997 present value dollars) to people born before 1917, and will deliver another $1.8 trillion to people born between 1918 and 1937. But young and future workers cannot necessarily do better by investing their payroll taxes in capital markets. If the old system were closed down, massive unfunded liabilities of $9-10 trillion would still have to be paid unless already accrued benefits were cut. Alternative methods of calculating these accrued benefits yield somewhat different numbers: the straight line calculation is $800 billion less than the constant benefit calculation we propose as the benchmark. Using this benchmark in a world with no uncertainty, we show that privatization without prefunding would not increase returns at all, net of the new taxes needed to pay for unfunded liabilities. These new taxes would amount to 3.6 percent of payroll, or about 29 percent of social security contributions. Prefunding, implemented by reducing accrued benefits or by raising taxes, would eventually increase money's worth for later generations, but at the cost of lower money's worth for today's workers and/or retirees.

Computing money's worth when there is uncertainty is much more difficult unless four conditions hold, namely optimization, time homogeneity, stable prices, and spanning. Under these conditions, the diversification of social security investments into stocks and out of bonds has no effect whatsoever on money's worth when it is properly adjusted for risk: a dollar of stock is worth no more than a dollar of bonds. When spanning fails, diversification can raise welfare for constrained households, but the exact money's worth must depend on specific assumptions about household attitudes toward risk. Calculations like those of the Social Security Advisory Council that attribute over $2.85 of net present value gain to each $1 shifted from bonds to stocks completely overlook the disutility of risk. By contrast, we estimate that a 2 percent of payroll equity fund carved out of social security would increase net present value by about 59 cents per dollar of bonds switched into equities, instead of $2.85. When the likely reductions in income and longevity insurance are factored in, the net advantage of privatization and diversification is substantially less than popularly perceived.

Number of Pages in PDF File: 72

JEL Classification: H0, E6, G1

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Date posted: February 4, 1999  

Suggested Citation

Geanakoplos, John and Mitchell, Olivia S. and Zeldes, Stephen P., Social Security Money's Worth (August 1998). Columbia Business School, PaineWebber Working Paper No. PW-98-05. Available at SSRN: http://ssrn.com/abstract=145910 or http://dx.doi.org/10.2139/ssrn.145910

Contact Information

John Geanakoplos
Yale University - Cowles Foundation ( email )
Box 208281
New Haven, CT 06520-8281
United States
203-432-3397 (Phone)
203-432-6167 (Fax)
HOME PAGE: http://cowles.econ.yale.edu/P/au/d_gean.htm
Olivia S. Mitchell
University of Pennsylvania - The Wharton School ( email )
Philadelphia, PA 19104-6365
United States

National Bureau of Economic Research (NBER)
1050 Massachusetts Avenue
Cambridge, MA 02138
United States
Stephen P. Zeldes (Contact Author)
Columbia Business School - Finance and Economics ( email )
3022 Broadway
Uris 825, Dept. of Finance & Economics
New York, NY 10027
United States
212-854-2492 (Phone)
212-208-4699 (Fax)
HOME PAGE: http://www.columbia.edu/~spz1

National Bureau of Economic Research (NBER)
1050 Massachusetts Avenue
Cambridge, MA 02138
United States
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