Fixed-effects and related estimators for correlated random-coefficient and treatment-effect panel data models

I derive conditions under which a class of fixed-effects estimators consistently estimates the population-averaged slope coefficients in panel data models with individual- specific slopes, where the slopes arc allowed to be correlated with the covariates. In addition to including the usual fixed-effects estimator, the results apply to estimators that eliminate individual- specific trends. I apply the results, and propose alternative estimators, to estimation of average treatment in a class of nonlinear unobserved-effects models.