Table II.B1 shows the income, cost, and asset reserves for the OASI, the DI, and the combined OASI and DI Trust Funds in calendar year 2018.
Interest earned on invested trust fund asset reserves accounted for 8.3 percent of OASI and DI combined trust fund income in 2018. Revenue 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 accounted for 3.5 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 $3.1 billion during 2018 because income to the combined funds, including interest earned on trust fund reserves, exceeded total cost. In last year’s report, combined reserves were projected to start declining in 2018. At the end of 2018, the combined reserves of the OASI and the DI Trust Funds were $2,895 billion, or 273 percent of estimated cost
2 for 2019. In comparison, the combined reserves at the end of 2017 were 289 percent of actual cost for 2018.