Despite Social Security's success at bolstering retirement security, many older Americans remain mired in poverty. Because Social Security does not guarantee a minimum benefit, many long-service, low-wage workers receive benefits that leave them below the poverty line. African Americans, Hispanics, and unmarried women are especially vulnerable. Although productivity gains are likely to reduce old-age poverty over time, Social Security's long-term financing problem makes future benefit cuts likely. This analysis explores two potential minimum-benefit designs and shows that an effective minimum benefit could help protect the highest-risk groups.