Longevity Risk: The Risk of Outliving Your Money

It is the strangest risk in finance: the bad financial outcome is the good life outcome. And it is systematically underestimated for a specific, fixable reason — people plan around average life expectancy, and by definition roughly half of people outlive the average. A retirement plan built to the average fails in half the futures it was built for.

Why averages mislead here

Life expectancy is usually quoted from birth, but what matters for retirement is conditional life expectancy — how long someone who has already reached 65 will live. Those numbers are higher, because reaching 65 means having survived everything before it. According to US Social Security Administration data, a man reaching 65 can expect on average to live to about 83 and a woman to about 85 — and roughly one in four 65-year-olds will live past 90. Averages also hide the spread: the planning question is not "when will the average person die" but "what if I'm in the long tail?" For a couple, the relevant horizon is the second death, which is later still — the probability that at least one of two 65-year-olds reaches 90 is substantially higher than for either alone.

How longevity risk interacts with the other retirement risks

Longevity risk is a multiplier on everything else in this pillar. A longer horizon gives sequence-of-returns risk more room to do damage and forces withdrawal rates lower — the research behind the 4% shorthand assumed 30 years, and a 65-year-old planning to 95 is already at that boundary, while an early retiree is far beyond it. It also compounds inflation risk: over 30 years, even 3% inflation cuts the purchasing power of a fixed payment by more than half. And it is the risk that individual saving handles least efficiently — you must self-insure the worst case, holding enough for a 30-year retirement you may not have — which is precisely the gap that pooled solutions exist to address.

The frameworks used to manage it

Plan to a percentile, not the average. Actuarial practice plans to a conservative horizon — for instance the age only 25% or 10% of retirees will outlive — rather than the mean. For a 65-year-old today that typically means planning into the early-to-mid 90s. The SSA publishes a life expectancy calculator and a research-grade Longevity Visualizer for exactly this kind of exploration.

Pool the risk. Lifetime income streams — state pensions, employer defined-benefit pensions where they survive, and lifetime annuities — transfer longevity risk to an institution that can pool it across many lives. This is the one problem annuities genuinely solve, with all the cost and counterparty caveats covered in that article.

Keep growth assets in the plan. A horizon that may run 30+ years is long-term money; portfolios de-risked entirely into cash-like assets at retirement expose the later decades to inflation instead of markets. Glide paths that retain equity exposure are one response — a tradeoff against sequence risk, not a free lunch.

Preserve flexibility. Housing equity, the ability to adjust spending, and part-time work capacity all function as informal longevity buffers. None of these frameworks is a recommendation; they are the standard toolkit the field uses to think about a risk that cannot be predicted for any individual.