Social Security is largely a pay-as-you-go program. Most of the payroll taxes collected from today's workers are used to pay benefits to today's recipients. In 2011, the Old-Age and Survivors Insurance and Disability Insurance Trust Funds collected $805.1 billion in revenues. Of that amount, 82.8% was from payroll tax contributions and reimbursements from the General Fund of the Treasury and 3.0% was from income taxes on Social Security benefits. Interest earned on the government bonds held by the trust funds provided the remaining 14.2% of income. Assets increased in 2011 because total income exceeded expenditures for benefit payments and administrative expenses.