Definition

A Cost-of-Living Adjustment (COLA) is an annual percentage increase applied to pension annuities or Social Security benefits to offset the eroding effects of inflation. It is commonly tied to the Consumer Price Index (BLS CPI-U or CPI-W).

Actuarial Compounding Formula

When a pension plan incorporates an annual compound COLA of rate g, the payment in year t is: 

P(t) = P(0) × (1 + g)^t

Over a 25-year retirement, a 2.5% annual compound COLA increases monthly cash flow by +85.4% compared to an unindexed corporate pension, adding hundreds of thousands of dollars in lifetime Pension Net Present Value.

Types of Pension COLAs

  • Full CPI Indexing: Payments match 100% of the annual CPI increase (common in military and some state public retirement systems).
  • Capped COLA: Increases are bounded by an annual ceiling (e.g. CPI up to a maximum of 2% or 3% per year).
  • Diet COLA: Applied in federal FERS pensions, where the adjustment equals CPI minus 1% if inflation exceeds 3%.
  • Fixed Annual Increment: A guaranteed fixed step-up (e.g. 1.5% annually) regardless of external inflation metrics.
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