SPRINGFIELD, Ill. (CBS) — Illinois public school teachers and retirees could have reason to worry about the kinds of pension checks they will be getting down the line.

As WBBM Newsradio’s Bernie Tafoya reports, the state has been writing IOUs to the Illinois Teachers Retirement System for decades, underfunding the pension system.

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LISTEN: WBBM Newsradio’s Bernie Tafoya reports

Now, that pension fund is saying the situation may be so bleak that even currently retired teachers might have to take a hit.

The Springfield State-Journal register reported over the weekend that pension director Dick Ingram sent a memo to his board on Feb. 9, saying he was no longer confident that the state’s largest pension system will continue to pay it enough money to stay above water. The state owes Ingram’s fund $43 billion.

He cited one forecast that the Teachers Retirement System could be insolvent by 2029.

Ingram said pension funding is under severe threat from the state’s unpaid bills, soaring Medicaid costs and the $85 billion in overall unfunded pension liability, which is expected to rise.

“If that is the case, the only other option available that would significantly change the amount owed is to reduce past service costs for active members and retirees,” Ingram wrote in the memo.

In an interview with the newspaper Friday, Ingram said the state might have to target cost-of-living pension increases, which are currently 3 percent a year and compounded.

“I’m really stuck,” he told the paper. “I have to say that the math is not trueing up with what is constitutional or fair or earned or whatever else.”

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Will Lovett, a lobbyist for the Illinois Education Association, said changing benefits for those who have already retired is unconstitutional.

“That is crystal clear in that benefits cannot be modified or changed,” he said.

The Illinois House Republican leader, Rep. Tom Cross (R-Oswego), praised Ingram’s shift in thinking but declined to endorse the idea of altering benefits for those already receiving them.

“I’ve never had members of the General Assembly advocate that,” Cross said. “You’re in a whole different arena with retirees.”

Ingram said that lawmakers have told him the state is unlikely to continue making full pension payments to the fund. As a result, Ingram had a consulting firm to try to determine when the fund could become insolvent. It concluded that it could happen between 2029 and 2049.

Gov. Pat Quinn addressed the pension crisis shortly after releasing his budget plan in February.

“The system is going to be strengthened and stabilized, and everyone has an interest in that, especially the employees,” Quinn said in February. “You can’t have a pension system that goes bust, and we won’t permit that to happen in Illinois.”

“Everybody is going to get a haircut. No one will get scalped – that’s the basic concept,” the governor added.

The governor wouldn’t predict what the haircut will look like.

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