Alternative methods for evaluating the impact of interventions

This chapter considers the problem of estimating the impact of interventions in the presence of selection decisions by agents. For specificity we focus on the problem of estimating the impact of training on earnings when the enrollment of persons into training is the outcome of a selection process. The analysis of training presented here serves as a prototype for the analysis of the closely related problems of deriving selection-bias-free estimates of the impacts of unionism, migration, job turnover, unemployment, and affirmative action programs on earnings.