If entry effects are detected, the validity of a random-assignment evaluation for the sample of applicants may be questioned. When entry effects are present, the number and characteristics of applicants are different than they would have been in the absence of welfare reform. As a result, impact estimates from the sample of applicants do not necessarily apply to the cases that would have applied for assistance had welfare reform not been implemented in the research sites. Nonetheless, as noted previously, impact estimates would remain unbiased for the population of actual applicants. If entry effects are small, impact estimates for applicants may still provide a good indication of the effects of the experimental policies on cases that would have applied for assistance in the absence of welfare reform.
Entry effects do not call into question a random-assignment evaluation's results for recipient cases. This is because, when welfare reform is implemented, recipient cases are already on welfare.