Mercer reported Monday that the funding levels of pension plans sponsored by S&P 1500 companies fell by 1% in April to 84%.
That left a collective deficit of $360 billion as of April 30, up $28 billion from March and up from $257 billion at the beginning of the year.
Mercer estimated that aggregated assets of the S&P 1500 constituents stood at $1.84 trillion through the end of April, compared with aggregate liabilities of $2.2 trillion.
Equity market gains did not offset the liability growth of pension plan sponsors, according to Mercer. The S&P 500 index earned about 0.6% during April.
The Mercer Yield Curve discount rate for mature pension plans fell by 11 basis points to 4.17%, its lowest point in almost a year, driving liabilities upward.