This section classifies which type of policy evaluations this paper performs, how its model relates to the generalized Roy model, what the challenges are and how they are addressed.
The task that the authors set for themselves is the first of the three evaluation tasks set out by \citealt{Heckman_2007}: They evaluate SNAP in its existing form on the eligible population.
The population of interest are eligible children. The treatment is whether the family participates in SNAP or not which is decided endogenously by the family. The authors start without any assumptions on the process by which treatment is selected or how health is affected by observable characteristics, the treatment or unobservables. Relating the notation of the paper to the notation from the Generalized Roy Model yields: