For a growing number of American cities and states, the obligations owed to retired public workers are consuming a share of annual budgets that leaves uncomfortably little room for the services those budgets are meant to fund. The arithmetic of pension funding, long discussed in actuarial reports few residents read, has become a practical constraint on what local governments can do, and the trajectory of the obligations is steeper than the trajectory of the revenues meant to cover them.

Public-sector pensions in the United States are largely defined-benefit promises, in which retired workers receive payments calculated from formulas tied to their years of service and final salaries. The promises were made over decades, sometimes more generously than the assumptions used to fund them anticipated, and were backed by contributions from employees, contributions from employers, and the investment returns earned on the assets in between. When all three lines align with the underlying obligations, the system funds itself with manageable strain on annual budgets. When they do not, the gap compounds.

The gap has compounded in many jurisdictions. Investment returns over long stretches have fallen short of the assumed rates used to discount the obligations, contributions from employers have lagged the actuarially required level, and benefit enhancements granted in better years were locked in even when conditions turned. The result is unfunded liabilities that, for some cities and states, run into the tens of billions of dollars, and annual pension costs that absorb a larger and larger share of general-fund spending each year.

For city managers and finance officers, the pressure is felt as a slow crowding out of everything else. Money that flows toward pension contributions is money that cannot fund road maintenance, libraries, public safety hiring, parks, or the other services residents most directly experience. As the pension share of the budget rises, the discretionary share falls, and decisions that once involved choosing among new investments increasingly involve choosing among reductions to existing ones. The effect is most acute in older industrial cities, whose tax bases have grown more slowly than their pension obligations.

The political economy of the problem complicates any solution. The benefits owed to current retirees and to workers who have already accrued years of service are in most jurisdictions protected by constitution or contract, leaving little room to reduce them retroactively. Changes to future benefits affect future hires or unaccrued portions of current employees’ entitlements, but their effects on funding gaps unfold over decades. Raising contributions imposes costs on workers and on taxpayers who may already feel stretched, while raising taxes to fund obligations made years ago is a hard message to deliver to current residents who did not vote for the original promises.

Investors who buy municipal debt have begun to discriminate more sharply on the basis of pension health. Cities and states with deep funding gaps face higher borrowing costs and greater scrutiny when they come to market, with credit-rating actions tied increasingly to the trajectory of pension obligations rather than to short-term budget outcomes alone. The higher cost of capital then adds another claim on operating budgets that already struggle to keep pace with retirement-related demands, tightening the loop in which fiscal pressure feeds on itself.

Some jurisdictions have made progress by raising contributions, smoothing recognition of investment volatility, and adjusting benefits at the margins for future service. Others have leaned on accounting choices that defer rather than resolve the underlying gap, postponing the day when contributions must rise sharply or services must contract. The difference between approaches that engage the problem and those that defer it is increasingly visible in long-run budget projections, even when short-term financial statements look similar.

The wider risk is that pension pressure becomes self-reinforcing for the cities least able to absorb it. As services contract under the weight of retirement costs, residents and businesses become more likely to relocate, eroding the tax base on which both pension contributions and operating budgets depend. A city that loses population because its services have weakened then has fewer resources to fund the obligations that prompted the weakening, a dynamic that has shadowed the most acute cases. Avoiding it requires sustained engagement with arithmetic that does not bend to political convenience, and the willingness of state and local leaders to confront a problem whose origins predate them and whose resolution will outlast their terms.