M & K Employee Solutions v. Trustees of the IAM National Pension Fund

Under the Employee Retirement Income Security Act (ERISA), pension plans may calculate an employer's withdrawal liability — the payment owed when a company stops participating in an underfunded multiemployer pension plan — using actuarial assumptions selected after the statutory measurement date (the last day of the plan year before the employer's withdrawal). Justice Ketanji Brown Jackson authored the unanimous opinion of the Court. ERISA's Section 1391 requires that withdrawal liability be calculated based on the plan's unfunded vested benefits (UVBs — the gap between what a pension plan owes workers and what it actually has) "as of" the measurement date. The phrase "as of" fixes the reference point for hard factual inputs, like the number of plan participants and the value of plan assets, to that date. But actuarial assumptions — such as discount rates, which are interest rates used to convert future benefit payments into present-day dollar values — are not observable facts about the plan. They are predictive tools that actuaries select for the purpose of performing a specific calculation. Because they function as calculation tools rather than factual data, the "as of" requirement does not freeze them to the measurement date. Section 1393, which directly governs the selection of actuarial assumptions, imposes no deadline for choosing those assumptions and requires only that they be "reasonable" and reflect the actuary's "best estimate of anticipated experience under the plan." Courts do not read deadlines into statutes that contain none, especially when Congress imposed timing limits on actuarial assumptions elsewhere in ERISA (§1399) but chose not to do so in §1393 — a deliberate omission. Locking actuaries into assumptions chosen before the measurement date could actually force them to use outdated data, since current market and plan-performance information may not be available until after that date, directly undermining the "best estimate" standard Congress mandated. Employers' concerns about potential manipulation are addressed by ERISA's existing requirement that assumptions be reasonable and by employers' right to challenge unreasonable assumptions through arbitration — not by reading additional restrictions into the statute.