The Social Security Trust Fund, comprising the Old-Age and Survivors Insurance (OASI) and Disability Insurance (DI) funds, held roughly $2.9 trillion in 2021 to pay for retirement and disability benefits. Financed by payroll taxes, the surplus is invested in special non-marketable U.S. government bonds, effectively lending the money to the federal government for other spending. However, the program's costs have exceeded its non-interest tax income since 2010, and the Social Security Trustees project the Trust Fund could be exhausted by 2035. If that occurs, incoming payroll taxes would only cover about 83% of promised benefits. To address this looming shortfall, policymakers have proposed solutions such as raising the retirement age, increasing taxes, or diversifying investments.