Hello,

I want to estimate a Cobb-Douglas production function with Stata's opreg command as explained here:
https://journals.sagepub.com/doi/pdf...867X0800800204

Can anyone tell me where to put exogenous regressors because they are very relevant in my study?
I suppose they should appear in equation (7) in the paper cited above along with age and capital, which would mean in the state() option. Is that correct?

Unfortunately if I try this most of them are simply omitted from the final output table, which I do not understand. Those regressors have many zeros if this has any consequence in opreg.
There are no such problems using any other estimation strategy like OLS, FE or GMM. I can provide further information if needed.

Best regards,

Tim