In August 1996, welfare reform legislation was passed and the Census Bureau was mandated to conduct a survey to evaluate welfare reform and its impact on the nation. The Survey of Program Dynamics (SPD), a longitudinal demographic survey, is designed to accomplish that goal. The SPD uses a sample of original respondents from the 1992 and 1993 panels from the Survey of Income and Program Participation (SIPP). The SPD is conducted each Spring from 1997 through 2001.