How Public Sector Pensions Work: Promises, Funding Gaps, and Reform
A pension promised to a public employee today is typically paid decades later, funded by money invested long before the payout is due. When that math falls short, the resulting gap becomes one of the harder problems in state and local budgeting.
Published July 6, 2026Most state and local government employees — teachers, police officers, firefighters, and general civil servants — are covered by defined benefit pension plans, which promise a specific retirement payout based on salary and years of service, rather than defined contribution plans like a 401(k), where the eventual payout depends on how much was contributed and how investments performed. This distinction matters because a defined benefit promise is a fixed obligation regardless of how the underlying investments perform, which shifts the investment risk onto the government and, ultimately, taxpayers, rather than onto the individual employee.
How a pension fund is supposed to work
In theory, a pension system funds itself through a combination of employee contributions, employer (government) contributions, and investment returns on the accumulated fund over an employee's entire career, with the goal of having enough assets set aside by the time an employee retires to cover their promised payments for the rest of their life. Actuaries calculate how much needs to be contributed each year based on assumptions about future investment returns, employee lifespans, and salary growth, and a fund is considered "fully funded" when its assets are projected to cover the future obligations those assumptions imply.
Where the funding gaps come from
Unfunded liabilities — the gap between what a pension system has promised and the assets it holds to pay for those promises — have become a significant and recurring issue tracked by groups like the National Association of State Retirement Administrators for many state and local governments. These gaps generally build up through some combination of governments underfunding their required annual contribution during tight budget years, investment returns falling short of the assumed rate over a sustained period, and benefit enhancements granted during good economic times without a corresponding increase in funding to pay for them. Because pension obligations compound over decades, a funding shortfall that starts small can grow substantially if it goes uncorrected across multiple budget cycles.
The assumed rate of investment return is itself a frequent point of dispute. A pension fund that assumes a higher long-term return can report a smaller funding gap on paper, since future obligations are discounted more heavily, but if actual returns fall short of that assumption over time, the true funding shortfall turns out to be larger than reported. Critics of overly optimistic return assumptions argue they mask the real scale of the problem, while defenders point out that historical long-term market returns have, over sufficiently long periods, been broadly consistent with the assumptions many funds use.
Who ultimately bears the cost
Because public pensions are typically protected by state constitutional or contractual provisions once earned, governments generally cannot simply reduce benefits already promised to current retirees or accrued by current employees, even when a fund is significantly underfunded. This means closing a funding gap usually falls to some combination of increased government contributions, which competes directly against the same pool of revenue examined in how municipal debt and local budgets work, alongside other priorities like schools, infrastructure, and public safety spending, and changes to benefits for future, not-yet-hired employees, since new hires are not protected by the same accrued benefit guarantees.
Common reform approaches
States facing large unfunded liabilities have pursued a range of changes: raising the retirement age or reducing benefit formulas for newly hired employees, increasing required employee contributions, moving new hires into hybrid plans that combine a smaller defined benefit with a defined contribution component, or, in some cases, issuing pension obligation bonds to inject a lump sum into the fund in hopes that investment returns outpace the bond's interest cost. Each approach carries tradeoffs — reducing benefits for future hires does little to close a near-term funding gap driven by current retirees, while pension obligation bonds add new government debt and carry real risk if investment returns underperform the assumed rate. There is no single reform that resolves the underlying tension between a decades-long promise and the year-to-year budget pressures governments actually face.
Why the issue rarely gets resolved quickly
Part of what makes public pension funding such a persistent policy problem is the mismatch between political time horizons and the actuarial time horizons involved. A benefit enhancement granted today may not create a visible funding strain for a decade or more, well past the term of the officials who approved it, while the cost of correcting an underfunded system falls on whichever future officials happen to be in office when the shortfall becomes unavoidable. That asymmetry, more than any single policy choice, is why pension funding gaps tend to accumulate gradually over long stretches before finally becoming an urgent budget crisis that forces difficult tradeoffs all at once.