This paper proposes a nonparametric method of estimating marginal treatment effects in heterogeneous populations. Building upon an insight of Heckman and Vytlacil, the conventional treatment effects model with heterogeneous effects is shown to imply that outcomes are a nonlinear function of...

The reform of the cash-based welfare program for single mothers in the US which occurred in the 1990s was the most important since its inception in 1935. The reforms imposed credible and enforceable work requirements into the program for the first time, as well as establishing time limits on...