Social Security is widely portrayed as a self-financed program with a long-term trust fund solvency problem. But for more than a decade, the program has already been financed in part through federal borrowing. The trust fund is a political construct, not a true repository of savings or investments. Since 2010, the Treasury has borrowed more than $1.5 trillion to pay Social Security benefits, and borrowing is projected to rise sharply even before the trust fund is exhausted in 2032. Over the next 75 years, the program’s cash-flow shortfall will exceed $28 trillion in present-value terms.