The new year will see an increase in the amount Illinois pays into the state's five publicly-funded pension systems.

Illinois' auditor general on Wednesday released a report by the state actuary showing a more than $680 million increase in pension payments in 2015 to $7.5 billion.

The report doesn't explain the increase. However, it noted three of the five pension systems lowered the estimated rate of return they expect from investments.

Pension systems get their money through employee contributions, state contributions and investment income. When investment income lags, higher state contributions are made.

Illinois lawmakers last fall increased employee contributions and reduced benefits such as cost-of-living adjustments to close a $111 billion pension deficit. The Illinois Supreme Court will decide whether the action is constitutional.