Re: st: treatreg vs ivreg revisited

[Andrea Menclova <andrea.menclova@canterbury.ac.nz>]

Many thanks for your helpful response.  However, I am still confused on a couple of points and I am hoping you would be kind enough to answer them.

 

1. When you say I should “ never rely on the inverse Mills ratio for addressing endogeneity/selection", are you saying I should always estimate an IVmodel in addition to the treatment effects model, and not rely solely on the inverse Mills ratio approach?

 

2. Is a treatment effects/”treatreg” approach valid even if the instrument(s) are “weak?”  Are there any tests for the validity of instruments in the context of a treatment effects/”treatreg” model?

 

I appreciate your help and time,

 

Andrea