While Illinois' woefully underfunded state-employee pensions have been a topic of discussion all year, there have been just a handful of concrete proposals. This week, four Illinois professors added to the list, coming forward with their own idea for the State Universities Retirement System, known by the acronym SURS. The plan calls for Illinois to end its long practice of not taxing retirement income, and it warns of tuition increases no matter what sort of pension plan is implemented. Illinois Public Radio’s Brian Mackey spoke with one of the authors of that plan, University of Illinois Professor Avijit Ghosh. They began by talking about the constitutional question looming over the pension debate.