Social Security’s long-term shortfall is likely significantly worse than projected. In 2025, the Social Security Trustees estimated that the program faces a 75-year funding shortfall equal to $27 trillion in present-value terms. But those projections rely on unusually optimistic assumptions about future US fertility rates. The Trustees are likely understating Social Security’s insolvency problem by assuming Americans will start having far more children than current trends suggest.

If fertility instead follows projections from the Congressional Budget Office (CBO) or the US Census Bureau, Social Security’s 75-year deficit rises to at least $30 trillion. In other words, the Trustees and the Social Security Administration (SSA) may be understating the size of Social Security’s long-term financing gap by at least $3 trillion in present value terms.

Examining Social Security’s Fertility Rate Assumptions









Consequences of the Trustees’ Optimistic Projection







Congress Should Demand Answers

The Trustees’ fertility assumptions are not a technical footnote. Because Social Security is financed on a pay-as-you-go basis, fertility projections directly shape estimates of the program’s long-run solvency. If the Trustees’ fertility assumptions are too optimistic, then Social Security’s financing gap is significantly larger than official projections suggest. 

As Congress debates Social Security reform, it should be wary of relying on demographic assumptions that are substantially more optimistic than those used by other government forecasters. Policymakers risk basing reform decisions on projections that overestimate the future size of the workforce and, in turn, the program’s future revenue base. At a minimum, lawmakers should explore why the Trustees’ fertility projections appear to be such outliers, and the Social Security Advisory Board should reconvene the Technical Panel on Assumptions and Methods to better assess the fertility rates likely to occur in the US in the future.

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