Calculating Illinois' unfunded pension debt is a job only an actuary can love. But it's vital because pensions are the biggest piece of state government's liabilities, a total that a respected civic group estimates is $106 billion.

You start with assumptions about investment returns, interest rates, salary growth rates and estimates about the longevity of state workers. There's ample room for different results.

The Civic Committee of the Commercial Club of Chicago, relying on state data and input from Aon Consulting actuaries, placed the pension liability at $46 billion. Add to that another $10 billion in bonds the state has issued to pay short-term pension costs.

Gov. Blagojevich's budget office argues the Civic Committee's $46 billion figure is too high. A spokeswoman said the current liability is $40.7 billion.

However, the Legislature's bipartisan Commission on Government Forecasting and Accountability last placed the liability at $42.2 billion. That comes from a pension report issued in August.

The agency's executive director, Dan Long, said pension liabilities are a moving target. But whatever the figure, the situation is serious, he said.

In a November report issued with the backing of labor unions, the nonpartisan Center for Tax and Budget Accountability used the $42.2 billion figure. It warned that Illinois' pension debt was worse than the liability of any other state. California, for example, with more than three times the Illinois population, carries a liability of only $25.5 billion, the report said.

Like the Civic Committee, the center recommended increasing the individual income tax and expanding the sales tax base to deal with the issue. But it differed from the business-backed Civic Committee by calling for a new tax on carbon emissions.

The Civic Committee proposed an increase in the corporate income tax but the center did not. The center rejected suggestions that the state move its employees from a traditional defined-benefit pension plan to a defined-contribution program similar to those embraced by private businesses.

-- Sun-Times News Group State's budget meltdown