Table
II.B1 shows the income, expenditures, and asset reserves for the OASI, the DI, and the combined OASI and DI Trust Funds in calendar year 2017.
Four percent of OASI and DI combined Trust Fund income in 2017 came from subjecting up to 50 percent of Social Security benefits to Federal personal income taxation for beneficiaries with income (including half of benefits and all non-taxable interest received) exceeding specified levels. Interest earned on invested trust fund asset reserves accounted for 9 percent of OASDI income. The remaining income to the combined OASI and DI Trust Funds, less than 0.01 percent, came from reimbursements from the General Fund of the Treasury.
1
The trust fund investments provide the basis for paying benefits. Combined trust fund reserves increased by $44.1 billion for 2017 because income to each fund, including interest earned on trust fund reserves, exceeded total expenditures. At the end of 2017, the combined reserves of the OASI and the DI Trust Funds were $2,892 billion, or 288 percent of estimated expenditures
2 for 2018. In comparison, the combined reserves at the end of 2016 were 299 percent of actual expenditures for 2017.