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Heckman selection model singular matrix

Posted: Fri Aug 24, 2018 8:38 pm
by Lalan_dk
Hi there,

I have problem with near singular matrix in heckman estimation. I think I don't have dummy variable trap problem. I don't know what the problem is. Maybe anyone can help me?

I run estimation with following command:

Code: Select all

smpl if ar02b=1 and h_income<>NA
equation milk_exp.heckit(2step) exp_milk  h_income head_age head_educ  elder_n children_n @ buy_milk   head_educ  elder_n children_n free_milk


And here the workfile attached