Poorly funded pension plans for state and local public employees saw their finances erode in recent years despite strong investment returns, as the gulf between states with better and worse-off retirement systems has grown wider.

These findings are presented in a new report from The Pew Charitable Trusts that surveys the health of state-run public pension systems.

The current economic expansion in the U.S., which began in June 2009, is now the longest on record at about 121 months. It has unfolded in the wake of the Great Recession, which took a heavy toll on state and local budgets and the financial health of their pension systems.