These pie charts illustrate the composition of our federal budget. If you put your cursor over an individual category you'll see the category's value in dollars and as a percentage of total federal spending or revenue. The four largest sources of spending -- Health, Social Security, Defense, and Income Security -- constitute over 75% of annual expenditures. While the government brings in most of its revenue from income taxes and social insurance taxes, the second pie chart demonstrates that the deficit is similar in size to these revenue sources. As a result, our government spends a significant part of the budget on annual interest, a percentage that will continue to grow as deficits accumulate and debt increases.