Market Valuation of Accrued Social Security Benefits

31 Pages Posted: 21 Jul 2009 Last revised: 12 Aug 2009

See all articles by John Geanakoplos

John Geanakoplos

Yale University - Cowles Foundation

Stephen P. Zeldes

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

Multiple version iconThere are 2 versions of this paper

Date Written: July 2009

Abstract

One measure of the health of the Social Security system is the difference between the market value of the trust fund and the present value of benefits accrued to date. How should present values be computed for this calculation in light of future uncertainties? We think it is important to use market value. Since claims on accrued benefits are not currently traded in financial markets, we cannot directly observe a market value. In this paper, we use a model to estimate what the market price for these claims would be if they were traded.

In valuing such claims, the key issue is properly adjusting for risk. The traditional actuarial approach - the approach currently used by the Social Security Administration in generating its most widely cited numbers - ignores risk and instead simply discounts "expected" future flows back to the present using a risk-free rate. If benefits are risky and this risk is priced by the market, then actuarial estimates will differ from market value. Effectively, market valuation uses a discount rate that incorporates a risk premium.

Developing the proper adjustment for risk requires a careful examination of the stream of future benefits. The U.S. Social Security system is "wage-indexed": future benefits depend directly on future realizations of the economy-wide average wage index. We assume that there is a positive long-run correlation between average labor earnings and the stock market. We then use derivative pricing methods standard in the finance literature to compute the market price of individual claims on future benefits, which depend on age and macro state variables. Finally, we aggregate the market value of benefits across all cohorts to arrive at an overall value of accrued benefits.

We find that the difference between market valuation and "actuarial" valuation is large, especially when valuing the benefits of younger cohorts. Overall, the market value of accrued benefits is only 4/5 of that implied by the actuarial approach. Ignoring cohorts over age 60 (for whom the valuations are the same), market value is only 70% as large as that implied by the actuarial approach.

Suggested Citation

Geanakoplos, John D and Zeldes, Stephen P., Market Valuation of Accrued Social Security Benefits (July 2009). NBER Working Paper No. w15170. Available at SSRN: https://ssrn.com/abstract=1435627

John D 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

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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