2SLS Regression

Two-Stage Least Squares is a two-step instrumental-variables estimator that addresses endogeneity, the situation where a regressor is correlated with the error term. In the first stage the endogenous regressor is predicted from instrumental variables, and in the second stage the structural equation is estimated using those predictions. It is a central tool in applied econometrics, developed in textbook treatments such as Angrist and Pischke (2009).