NISA Investment Advisors' Pension Surplus Risk index was 7.1% in April, down from 7.6% in March.
The decline was the second consecutive drop for the index and fourth in the past five months.
The volatility of the return-seeking asset component of the index fell to 7.6% from 7.9% over the one-month period, reaching its lowest reading since August 2014. The liability component of the index remained stable at 8.1%, but is down 2.1 percentage points from November's 10.2% reading.
The average plan funding ratio was 85.1% at the end of April, a 60 basis-point decline from March.
The index is a forward-looking estimate of the funded status volatility of the 100 largest corporate pension plans as determined by NISA from publicly available information.
