In the waiver process, there has been relatively little emphasis on selecting a representative set of sites in the negotiations for approval of welfare reform waivers. This is in large part because the federal staff recognize the administrative burdens of implementing random assignment and understand that it may not be feasible for all local welfare offices to assume these burdens. However, the lack of requirements concerning site selection has made it possible for states to select a set of sites that are most likely to implement the reforms successfully and to use the results from these sites to generalize to the rest of the state. Full implementation of the reforms statewide may then produce less positive results. It sometimes makes sense to implement new and untested programs in sites that are most likely to be successful, to determine if the approach is feasible under the best of circumstances. However, it is most useful to research and policy development if such motivations are stated explicitly and if evaluators and policymakers are then appropriately cautious in generalizing the results.
In addition, there may be a trade-off between a state's short-run interest in implementing the evaluation in sites where implementation is relatively easy and the state's longer-term interest. For instance, states that pay little attention to the representativeness of demonstration sites initially may become very concerned about this issue if impact estimates run counter to their expectations. DHHS can play a useful role in encouraging states to take a longer-term perspective on evaluation design, one that encompasses both implementation concerns and the potential ramifications of an unrepresentative group of sites.
We recommend that states, in their sampling plans, spell out the criteria used in selecting site (including whether the goal is approximate representativeness or selecting exemplary sites). We also recommend that states assess how representative the selected sites and their caseloads are of the state and its caseload as a whole. Wherever feasible, we recommend explicit sampling of sites, with some accommodation of administrative concerns (for example, very small sites or sites with special administrative difficulties could be excluded). Finally, we recommend that an analysis of the representativeness of the population in the sites (including both an updated analysis of site characteristics and a comparison of outcomes) be conducted after the fact, as well as during the site selection process. For example, in an intervention that is implemented statewide, but with random assignment in only selected demonstration counties, it may be useful to assess how similar the outcomes for the experimental group in the demonstration counties are to those in the state as a whole.