How do you measure and manage pension surplus volatility?

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AcadiFi · Accepted Answer

Pension surplus volatility measures the dispersion of funded status (assets minus liabilities) over a horizon, not just asset returns. The core formula: Var(Surplus) = Var(Assets) + Var(Liabilities) - 2·Cov(Assets, Liabilities). A plan with 12% asset volatility and 10% liability volatility but only 0.3 correlation has surplus volatility ≈ √(0.0144 + 0.01 - 0.0072) = 13% — higher than either leg alone. This counterintuitive result is why bonds-only plans are NOT risk-free if not duration-matched. Conversely, a well-matched LDI portfolio can have 15% asset volatility but 2% surplus volatility because asset and liability correlations approach 1 over short horizons. Surplus-at-Risk (SaR) at 95% is a 1-year loss in funded dollars: for a $6.2B plan with surplus volatility $800M, 1-year 95% SaR ≈ 1.645 × 800 = $1.32B. Funded-ratio volatility expresses the same metric as a percentage. Drivers to monitor: interest rate exposure (hedge ratio), credit spread (corporate discount vs Treasury holdings), inflation (for COLA plans), and longevity. Scenario analysis supplements VaR — '1994 bond massacre', 'COVID March 2020', 'UK LDI September 2022' stress tests reveal tail risks statistical models miss. Governance best practice: monthly surplus tracking, quarterly attribution (rates vs credit vs assets vs experience), annual asset-liability study, and triennial strategic review.

How do you measure and manage pension surplus volatility?

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