Ask an Actuary: What Pension Boards Should Know About Layered Amortization

By: Elizabeth Wiley, Cheiron

In the 2026 Public Retirement Systems Study, NCPERS collected detailed information about the amortization method, including, for the first time, whether plans use layered amortization.

This makes it a useful time to explain layered amortization, how it differs from open- and closed-single-pool approaches, and why the structure matters to boards.

Layered amortization is more than a mathematical technique. It is an organizational framework for how a pension plan records experience, schedules repayment, and reports progress.

What is amortization?

Wiley: Amortization is the process of paying down a debt or shortfall over time through regular payments. Anyone who has financed a car or home has experienced amortization. The payments may stay level or change over time, but each payment reduces the balance toward a target, typically zero.

Pension plans typically amortize the gap between a system’s actuarial liability for benefits already earned and the assets set aside to pay them. When liabilities exceed assets, this difference is an unfunded liability. When assets exceed liabilities, the plan has a surplus.

System-specific funding policies govern how the difference is amortized, including the payment structure, treatment of gains and losses, and the treatment of surplus.

This article focuses on whether experience is tracked and amortized as a single blended pool or as separate layers.

What is layered amortization?

Wiley: The NCPERS Study defines layered amortization as a variation of the closed method in which gains or losses, assumption changes, and plan amendments are tracked as separate bases or layers, each with its own closed amortization period.

This approach to organizing experience is key to the method’s governance value. Instead of combining all gains and losses into one balance, layered amortization tracks each layer separately, including its source, original amount, amortization period, remaining balance, and the payment or credit for the current year. It preserves a system’s total unfunded liability as the sum of the layers. Layered amortization does not change the amount being amortized. Instead, it changes how the system records experience, schedules repayments, and tracks progress over time.

Fixed payoff dates for each layer can strengthen funding discipline. Layering also promotes transparency and intergenerational equity by deliberately selecting amortization periods and payment patterns for different experience sources. These benefits depend on the design of the funding policy and the parameters adopted.

The method gives boards clearer information about the expected pattern of principal reduction and whether negative amortization is likely.

How is layered amortization different from open or closed amortization?

Wiley: With an open, or rolling, method, the repayment period resets at each valuation. A 20-year open period remains 20 years the following year. Each valuation replaces the prior amortization schedule with a new one based on the current unfunded liability. That may provide near-term smoothing, but it does not ensure a payoff date and can make it harder to see how past experience affected the unfunded liability and how it has been addressed over time.

With a closed, or fixed, single-pool method, a single repayment schedule applies to the total unfunded liability. A 20-year period becomes 19 years the following year, then 18, and so on, until the balance is paid off. That creates a clear finish line, but blends individual years and sources of experience into a single balance and schedule.

Layered amortization is a variation of closed amortization made up of multiple individual closed amortization bases. A plan often begins with an initial layer representing the unfunded liability at the time it transitions to layered amortization. Future gains, losses, assumption changes, and plan amendments then become new layers, each with its own closed repayment period.

Does layered amortization itself change the unfunded liability?

Wiley: Layered amortization affects how the unfunded liability is organized and paid down, but does not eliminate the unfunded liability, change promised benefits, alter trust assets, or make contributions sufficient.

The label matters less than the result. If amortization payments exceed the interest on the unfunded liability, the principal will decline. If the payment only covers interest, the plan treads water. And if payments are less than the interest, the unfunded liability is expected to grow even as contributions continue.

For layered amortization, boards should apply that test to the aggregate result so they understand whether the amortization policy will reduce the unfunded liability and on what schedule. Layered amortization improves governance by giving boards the information they need to answer this question.

Layering does not, by itself, create funding discipline. But, it gives boards better information to strengthen funding discipline beyond simply tracking progress toward eliminating the total unfunded liability. Because each layer has its own payoff date and schedule, boards can evaluate and manage each layer separately. For example, a board may choose to accelerate the repayment of a single layer to improve the plan’s funding and intergenerational equity while providing greater contribution stability than the existing schedule.

Why should I care if our unfunded liability is organized?

Wiley: A single-pool approach is like an odometer: it tells you the total miles, but not the route. Layered amortization is more like a route. It gives the same total balance, and also preserves the road taken, the investment and demographic experience, assumption changes, plan amendments, and other events that explain why the plan is where it is today.

That added visibility enables boards to ask better questions. A plan amendment, an investment loss, a demographic gain, and an assumption change may all affect the same total unfunded liability, but they raise different governance questions. Layering helps boards see those differences rather than losing them in a blended number.

Layered amortization can also help manage contribution volatility. Instead of amortizing new experience over the remaining years of a single-pool schedule, it assigns each new layer its own amortization period. This does not eliminate volatility, but it gives boards more flexibility and better information to manage the plan’s funding.

What should I know if my board is considering adopting layered amortization?

Wiley: Trustees do not need to memorize every possible parameter. Instead, they should ask what objectives the policy will accomplish, what tradeoffs it makes, and how the board will know whether it is working.

Boards might consider asking:

• Which sources of experience should be combined in layers?
• How long will each layer be amortized?
• Will payments be based on dollars or as a percentage of salaries?
• How will payment schedules change over time?
• Will shortfalls and surpluses be treated differently?
• What guardrails or adjustment rules should be considered for the policy to better align with the system’s objectives and risk tolerance? Should these be automatic or require board action?
• How will the board manage and monitor the transition? Is a prospective-only approach reasonable, or do unusual circumstances justify the added complexity of calculating retroactive layers?

Boards should also work with their staff and consultants to ensure they receive clear, useful reports showing each layer’s date, source, original amount, remaining balance and years, and the current-year payment or credit. If boards cannot easily understand the information, the governance benefits of layered amortization are reduced.

Finally, once adopted, the board should monitor and assess the amortization policy, revising it as appropriate as part of the overall system governance.

About the author: Elizabeth Wiley, FSA, EA, MAAA, FCA, is a consulting actuary for Cheiron with more than 21 years of experience working with public pension plans.

Her experience includes preparing GASB disclosures for public pension plans, analyzing ERISA, IRS regulations, and state legislation, valuation sensitivity analysis and asset/liability projections, and conducting actuarial audits of large public retirement plans.