Hello Everyone,

I am currently trying to estimate a gravity model for migrations and face a problem in the estimation of this one with the Heckman MLE (and two step in a second time).
When running it, Stata run the code but I have nothing more after "note: 33.origin#18.years omitted because of collinearity". I don't know if it difficulty converge or if it is taken into a "loop" or anything else...
Please find in attached files the .do to replicate the code. (I am currently struggling to import the .dta files)