The funded ratio of the U.S.’s 100 largest defined benefit pension plans dropped slightly in August, from 76.8 per cent as of July 31 to 75.3 per cent as of Aug. 31, the result of a $98 billion funded status decline, according to Milliman Inc.’s latest public pension funding index.

The result was driven by the month’s negative market performance, with the plans experiencing estimated aggregate investment returns of negative 1.6 per cent. Collectively, the plans lost around $74 billion in market value for the month, on top of a net negative cash flow of about $10 billion. Individual plans’ estimated August returns ranged from negative 2.4 per cent to negative 0.8 per cent.

Read: Bond yields, credit spreads led to DB pension solvency dips in Q3: reports

Also during the month, the deficit between the estimated assets and liabilities increased from $1.41 trillion at the beginning of the month to $1.508 trillion at the end of the month. The total pension liability continues to grow and stood at an estimated $6.099 trillion as of Aug. 31, up from $6.085 trillion as of July 31.

“With August’s results, only 17 of the 100 PPFI plans now stand over the 90 per cent funded mark, down from 19 last month,” said Becky Sielman, co-author of the index, in a press release. “However, the number of plans less than 60 per cent funded remained stable at 23.”

Read: Majority of Canadian DB pension solvency ratios above 100 per cent: report