IAM National Pension Fund

Rule Changes

As of May 2026: Respondent in Supreme Court case

When employers exit multiemployer pension plans, they owe a share of unfunded benefits—a calculation that hinges on assumptions about future investment returns. The IAM National Pension Fund changed its interest rate assumption from 7.5% to 6.5% in January 2018, weeks after the measurement date, and applied it retroactively to employers who had already withdrawn. The result: withdrawal liabilities tripled from $935 million to over $3 billion.

Updated May 22