<P> The Congressional Budget Office (CBO) reports the costs of mandatory spending programs in a variety of annual and special topic publications . Congress can affect spending on entitlement programs by changing eligibility requirements or the structure of programs . Certain entitlement programs, because the language authorizing them are included in appropriation bills, are termed "appropriated entitlements ." This is a convention rather than a substantive distinction, since the programs, such as Food Stamps, would continue to be funded even if the appropriation bill were to be vetoed or otherwise not enacted . </P> <P> The share of Federal spending for mandatory programs has been increasing as the U.S. population ages, while the discretionary spending share has fallen . </P> <P> CBO projects that spending for Social Security, Healthcare programs and interest costs will rise relative to GDP over the 2017 - 2027 period, while defense and other discretionary spending will decline relative to GDP . </P> <P> Over the past 40 years, mandatory spending for programs such as Medicare and Social Security has grown as a share of the budget and relative to GDP, while other discretionary categories have declined . Medicare, Medicaid and Social Security grew from 4.3% of GDP in 1971 to 10.7% of GDP in 2016 . </P>

Beginning with the largest category rank order the revenues and expenditures of the federal budget