In 2008, net contributions accounted for 83 percent of total trust fund income. Net contributions consist of taxes paid by employees, employers and the self-employed on earnings covered by Social Security. These taxes were paid on covered earnings up to a specified maximum annual amount, which was $102,000 in 2008 and is increased each year automatically (to $106,800 in 2009) as the average wage increases. The tax rates scheduled under current law for 2008 and later are shown in table II.B2.
Two percent of OASDI Trust Fund income came from subjecting up to 50 percent of Social Security benefits above specified levels to Federal personal income taxation, and 14 percent of OASDI income came from interest earned on investment of OASDI Trust Fund reserves. Social Security’s assets are invested in interest-bearing securities of the U.S. Government. In 2008, the combined trust fund assets earned interest at an effective annual rate of 5.1 percent. More than 98 percent of expenditures from the combined OASDI Trust Funds in 2008 went to pay retirement, survivor, and disability benefits totaling $615.3 billion. The financial interchange with the Railroad Retirement program resulted in a payment of $4.0 billion from the combined OASDI Trust Funds, or about 0.6 percent of total expenditures. The administrative expenses of the Social Security program were $5.7 billion, or about 0.9 percent of total expenditures.
Assets of the trust funds provide a reserve to pay benefits whenever total program cost exceeds income. Trust fund assets increased by $180.2 billion in 2008 because income to each fund exceeded expenditures. At the end of 2008, the combined assets of the OASI and the DI Trust Funds were 354 percent of estimated expenditures for 2009, down from an actual level of 358 percent at the end of 2007.
