A large and growing share of the federal budget goes to benefits for the nation's retirees, through Social Security, Medicare, Medicaid, and other programs; in addition, the exclusion of pension contributions and earnings from taxable income constitutes one of the largest preferences in the federal income tax system. CBO projects the budgetary impact of those policies under current law and analyzes a wide range of possible changes to those policies. (A separate page on Health Care provides additional information about CBO’s work in that area.)