IB#2006-21  

Abstract

We calculate the risk faced by defined benefit plan providers arising from uncertain aggregate mortality — the risk that the average participant will live longer than expected. First, comparing the widely cited Lee-Carter model to industry benchmarks, we show that plan providers appear to substantially underestimate the longevity of their employees. The resultant understatement of liabilities is 15.2 percent, when weighted by the characteristics of typical male participants in defined benefit plans, and reaches as much as 25.2 percent for male workers aged 22. Next, we consider the substantial mortality risk that arises even if plan providers were to use the Lee-Carter model or other unbiased forecasts of mortality reductions. We calculate the consequences for plan liabilities if aggregate mortality declines unexpectedly faster than is predicted by an unbiased projection. There is a 5 percent chance that liabilities of a terminated plan would be 2.9 to 5.1percent higher than what is expected, depending on the mix of workers covered. Lastly, we explain how longevity bonds might be used to transfer mortality risk from defined benefit plans to the capital markets, and we calculate a risk premium for a hypothetical frozen plan.

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Irena Dushi is an analyst at the U.S. Social Security Administration. Leora Friedberg is an economics professor at the University of Virginia. Anthony Webb is a research economist at the Center for Retirement Research at Boston College. The research reported herein was performed pursuant to a grant from the U.S. Social Security Administration (SSA) funded as part of the Retirement Research Consortium. The findings and conclusions expressed are solely those of the authors and do not represent the views of SSA, any agency of the Federal Government, the University of Virginia, or Boston College. Please send any inquiries to Anthony Webb at This e-mail address is being protected from spam bots, you need JavaScript enabled to view it The authors would like to thank Clark Burdick and Javier Meseguer at SSA for very helpful discussion, and Ed Burrows, Steve Sass, and Francis Vitagliano for their very helpful comments.