Corporate pensions’ funded status improved by $25 billion in June, according to Milliman Inc., on rising interest rates.

In spite of a $10 billion investment loss, the Pension Funding Index, which analyzes the 100 largest corporate defined-benefit plans, found a $35 billion liability reduction actually reduced the deficit to $186 billion from $211 billion at the end of May 2011.

"Normally when assets decline we're in for a fall in pension funded status, but not this month," John Ehrhardt, co-author of the Milliman Pension Funding Study, said in a press release. "In fact it's a rare combination: a funded status improvement driven by liabilities and in spite of a decline in assets.”