The spillover of welfare reform services to the control group was difficult to measure in the evaluations we reviewed. In Colorado's evaluation, welfare reform was implemented only in the demonstration counties; before implementation, there was concern that the provision of JOBS services to control cases would increase because welfare reform-related JOBS expansions would spill over to control cases in the research counties. Subsequent to implementation, the evaluator has been concerned that political pressures may be resulting in the displacement of services to control cases. The evaluators of Michigan's initiative suspected that some spillover had occurred because of the welfare reform program's strong emphasis on preparing individuals for employment, but they were unable to quantify these effects. (Presumably, the amount of spillover in Michigan's demonstration was reduced because caseworkers were assigned to serve only either experimental or control cases.) In Wisconsin, changing community institutions was a major goal of the WNW initiative; the likelihood of spillover to a control group through community effects was a major justification for the adoption of a nonexperimental design for the evaluation.