Stata 34 - Instrumental variable regression

[@shahrzadmadjlesi1017]

You explain tough issues through simple examples; It is a great job. Thank you so much.

[@sumitkumarmaji9158]

Thank you for the lucid explanation. I have one doubt. After the 1st stage when the endogenous variable y2 hat is determined, in the second stage, can we use some more exogenous (Xi) variables? Why I'm asking, that some of the exogenous variables may not be related to Y2 but important for Y1. So can we included them later in the second stage???