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...

A long-standing issue in the literature on education is whether marginal returns to education fall as education rises. If the population differs in its rate of return, a closely related question is whether marginal returns to higher education fall as a greater fraction of the population enrolls....

We estimate the trend in the transitory variance of male earnings in the U.S. using the Michigan Panel Study of Income Dynamics from 1970 to 2004. Using both an error components model as well as simpler but only approximate methods, we find that the transitory variance started to increase in the...