About 46 percent of American households will pay no federal individual income tax in 2011, roughly half of them because of structural features of the income tax that provide basic exemptions for subsistence level income and for dependents. The other half are nontaxable because tax expenditures special provisions in the tax code that benefit selected taxpayers or activitieswipe out tax liabilities and, in the case of refundable credits, yield net payments from the government. Provisions that benefit senior citizens and low-income working families with children particularly affect households with income under $50,000 but other factors make higher-income households nontaxable.