Knowledge of treatment effect heterogeneity or "essential heterogeneity" plays an important role in our understanding of how programs work and in the design of systems to allocate them among the eligible. This paper provides a relatively non-technical survey of the current state of the treatment...

This paper makes three contributions to the literature on program evaluation. First, we construct a model that is well-suited to conduct equilibrium policy experiments and we illustrate effectiveness of general equilibrium models as tools for the evaluation of social programs. Second, we...