Although the rules for public-employee pension funds vary, they operate under the same guidelines. Throughout their careers, teachers and other state and local employees contribute portions of their salaries into retirement funds managed by states and municipalities. In almost all cases, the employers also pitch in a percentage of the employees' salaries. Pension funds guarantee teachers, and their surviving spouses, regular payments after the employees' retirement. This article discusses the Illinois' teacher-pension fund deficit. At $20 billion in the red, the Illinois teacher-pension fund has the country's biggest deficit for such a fund, but it's not the only state with a problem. Faced with a tepid stock market, a rise in life expectancy, and teacher contracts that critics say inflate pensions, many states are seeking ways to tweak or even overhaul the way they underwrite educators' retirement benefits.