Defined benefit (DB) schemes increased their surplus over February when using realistic investment return assumptions, according to First Actuarial.
Under the firm's index, which uses best estimate expected returns on underlying assets, the combined surplus of the UK's 5,794 DB schemes grew by £13bn to £288bn last month.
In the same period, assets grew by £44bn to £1.5trn, while liabilities also increased at a slower pace by £31bn to £1.22trn.
The First Actuarial Best-estimate (FAB) index, launched in September last year, uses data underlying the Pension Protection Fund (PPF) 7800 index and the Purple Book.
It then calculates liabilities by switching this data to a set of assumptions using the actuarial firm's in-house ‘best estimate' assumptions, which are then adjusted to allow for full scheme benefits.
Last month, these assumptions included a weighted discount rate of 4.1%, an expected Consumer Price Index (CPI) inflation rate of 2.7%, and an estimated Retail Price Index (RPI) figure of 3.7%.
The figures are distinct from those put out by other indices, such as the PPF 7800 Index, which has shown deficits soar over the past year due to its reliance on gilt yields. The lifeboat fund's most recent figures showed the aggregate deficit had grown almost £50bn last month.
First Actuarial partner Rob Hammond said DB schemes were in a "healthier" position than otherwise painted.
"The FAB Index continues to buck the trend and contradict the doom and gloom headlines that others persistently promulgate," he said. "Over February 2017, asset performance was very strong, long-term inflation fell slightly, and long-term expected investment returns were relatively stable, resulting in a much healthier state of the UK's DB pension schemes than we would otherwise be led to believe.
"Only around 50% of the UK's 6,000 DB schemes' assets are held in bonds, so a fall in gilt yields is not the be-all and end-all when it comes to assessing the financial health of these schemes."
The index was designed to reduce "scaremongering" and help trustees better understand the value of liabilities.
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