LANSING – Michigan joined most of the rest of the nation in seeing its unfunded pension liabilities rise in 2015, according to a study released Thursday by the Pew Charitable Trusts.

Nationally, there was a $1.1 trillion gap between current pension fund revenues and promised benefits in 2015, the most recent year with complete data, the report said. That was a $157 billion increase from 2014.

The report blamed much of the increase on lower-then-expected investment returns, with the median being 3.6 percent.

“Many states face significant challenges in meeting pension promises to workers,” Greg Mennis, director of Pew’s public sector retirement project, said in a statement on the report. “The continued volatility and low investment returns are a reminder that policymakers cannot count on investment returns to close the pension funding gap.”

Michigan’s pensions were 64 percent funded in 2015, down from 67 percent in 2014, the report said, putting it in about the middle among the states.

Nationally, South Dakota had the best-funded pensions at 104.1 percent, though that was down from 107 percent in 2014. Pennsylvania had the least-funded at 55.8 percent, down from 60 percent in 2014.

Among the Great Lakes states, Wisconsin was top at 98.3 percent.

Only Alaska saw its funding ratio improve to 67 percent from 60 percent. Virginia held steady at 75 percent, the report noted.

Caleb Buhs, spokesperson for the Office of Retirement Services, said officials are reviewing the study and could not immediately comment on it.

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