Social Security is the single largest federal program, with outlays of $768 billion in fiscal year 2012. The program has two parts. The Old-Age and Survivors Insurance program pays benefits to retired workers and to their dependents and survivors, and the Disability Insurance program pays benefits to disabled workers and to their spouses and survivors. Social Security benefits are financed by a payroll tax on current workers, half paid by the worker and half paid by the employer. CBO regularly examines various possible changes to Social Security outlays or receipts.