IDEAS home Printed from
MyIDEAS: Log in (now much improved!) to save this paper

Stochastic Forecasts of the Social Security Trust Fund

Listed author(s):
  • Ronald D. Lee

    (University of California at Berkeley)

  • Michael W. Anderson
  • Shripad Tuljapurkar

    (Stanford University)

We present stochastic forecasts of the Social Security trust fund by modeling key demographic and economic variables as historical time series, and using the fitted models to generate computer simulations of future fund performance. We evaluate several plans for achieving long-term solvency by raising the normal retirement age (NRA), increasing taxes, or investing some portion of the fund in the stock market. Stochastic population trajectories by age and sex are generated using the Lee-Carter and Lee- Tuljapurkar mortality and fertility models. Interest rates, wage growth and equities returns are modeled as vector autoregressive processes. With the exception of mortality, central tendencies are constrained to the Intermediate assumptions of the 2002 Trustees Report. Combining population forecasts with forecasted per-capita tax and benefit profiles by age and sex, we obtain inflows to and outflows from the fund over time, resulting in stochastic fund trajectories and distributions. Under current legislation, we estimate the chance of insolvency by 2038 to be 50%, although the expected fund balance stays positive until 2041. An immediate 2% increase in the payroll tax rate from 12.4% to 14.4% sustains a positive expected fund balance until 2078, with a 50% chance of solvency through 2064. Investing 60% of the fund in the S&P 500 by 2015 keeps the expected fund balance positive until 2060, with a 50% chance of solvency through 2042. An increase in the NRA to age 69 by 2024 keeps the expected fund balance positive until 2047, with a 50% chance of solvency through 2041. A combination of raising the payroll tax to 13.4%, increasing the NRA to 69 by 2024, and investing 25% of the fund in equities by 2015 keeps the expected fund balance positive past 2101 with a 50% chance of solvency through 2077.

If you experience problems downloading a file, check if you have the proper application to view it first. In case of further problems read the IDEAS help page. Note that these files are not on the IDEAS site. Please be patient as the files may be large.

File URL:
Download Restriction: no

Paper provided by University of Michigan, Michigan Retirement Research Center in its series Working Papers with number wp043.

in new window

Length: 36 pages
Date of creation: Jan 2003
Handle: RePEc:mrr:papers:wp043
Contact details of provider: Postal:
P.O. Box 1248, Ann Arbor, MI 48104

Phone: (734) 615-0422
Fax: (734) 647-4575
Web page:

More information through EDIRC

References listed on IDEAS
Please report citation or reference errors to , or , if you are the registered author of the cited work, log in to your RePEc Author Service profile, click on "citations" and make appropriate adjustments.:

in new window

  1. Samwick, Andrew A., 1998. "New evidence on pensions, social security, and the timing of retirement," Journal of Public Economics, Elsevier, vol. 70(2), pages 207-236, November.
  2. Tuljapurkar, Shripad, 1992. "Stochastic population forecasts and their uses," International Journal of Forecasting, Elsevier, vol. 8(3), pages 385-391, November.
  3. Lee, Ronald & Tuljapurkar, Shripad, 1998. "Uncertain Demographic Futures and Social Security Finances," American Economic Review, American Economic Association, vol. 88(2), pages 237-241, May.
  4. Ronald Lee & Shripad Tuljapurkar, 1997. "Death and Taxes: Longer life, consumption, and social security," Demography, Springer;Population Association of America (PAA), vol. 34(1), pages 67-81, February.
  5. Ronald Lee & Shripad Tuljapurkar, 1998. "Stochastic Forecasts for Social Security," NBER Chapters,in: Frontiers in the Economics of Aging, pages 393-428 National Bureau of Economic Research, Inc.
  6. Cardarelli, Roberto & Sefton, James & Kotlikoff, Laurence J, 2000. "Generational Accounting in the UK," Economic Journal, Royal Economic Society, vol. 110(467), pages 547-574, November.
  7. Shripad Tuljapurkar & Carl Boe, "undated". "Mortality Change and Forecasting: How Much and How Little Do We Know?," Pension Research Council Working Papers 98-2, Wharton School Pension Research Council, University of Pennsylvania.
Full references (including those not matched with items on IDEAS)

This item is not listed on Wikipedia, on a reading list or among the top items on IDEAS.

When requesting a correction, please mention this item's handle: RePEc:mrr:papers:wp043. See general information about how to correct material in RePEc.

For technical questions regarding this item, or to correct its authors, title, abstract, bibliographic or download information, contact: (MRRC Administrator)

If you have authored this item and are not yet registered with RePEc, we encourage you to do it here. This allows to link your profile to this item. It also allows you to accept potential citations to this item that we are uncertain about.

If references are entirely missing, you can add them using this form.

If the full references list an item that is present in RePEc, but the system did not link to it, you can help with this form.

If you know of missing items citing this one, you can help us creating those links by adding the relevant references in the same way as above, for each refering item. If you are a registered author of this item, you may also want to check the "citations" tab in your profile, as there may be some citations waiting for confirmation.

Please note that corrections may take a couple of weeks to filter through the various RePEc services.

This information is provided to you by IDEAS at the Research Division of the Federal Reserve Bank of St. Louis using RePEc data.