This study uses the Urban Institute’s Dynamic Simulation of Income Model to project the share of Social Security beneficiaries whose retirement incomes fall below 75 percent of preretirement income, a common benchmark for a secure retirement. Absent significant Social Security reforms, we project the share of beneficiaries with inadequate retirement income will rise from 26 to 45 percent between 2020 and 2090. We show that working longer, saving more, and adding well-targeted minimum benefits to a bipartisan Social Security reform proposal could increase the share of beneficiaries with adequate retirement income by 19 percentage points, eliminate poverty at older ages, increase overall retirement incomes, and bolster government finances.