Taking apart the federal budget

President Obama's $3.8 trillion budget proposal for fiscal year 2011 includes billions to put people back to work and imposes new fees on some of the nation's largest banks.

The composition of tax revenue has shifted dramatically over the past 80 years. Individual and payroll taxes contribute about 80 percent of the total while the portion provided by corporate income taxes has fallen.

The federal budget can be divided into two types of spending. About one-third is "discretionary" — the portion of spending Congress decides every year. Two-thirds is "mandatory" — spending devoted to entitlement programs such as Social Security and Medicare.

As a percent of the total budget, the Defense Department takes up a smaller piece of the federal pie, while the proportion devoted to Health and Humans Services and Treasury has grown.

Since 1930, the federal government has run deficits in all but eight years. As a percent of the overall economy, the annual gap between spending and revenue is at its highest since WWII.