The reform of the cash-based welfare program for single mothers in the US which occurred in the 1990s was the most important since its inception in 1935. The reforms imposed credible and enforceable work requirements into the program for the first time, as well as establishing time limits on lifetime receipt. Research on the effects of the reform have shown it to have reduced the program caseload and governmental expenditures on the program. In addition, the reform has had generally positive average effects on employment, earnings, and income, and generally negative effects on poverty rates, although the gains are not evenly distributed across groups. A fraction of the affected group appears to have been made worse off by the reform.