Dear Stata users and experts,
I am running an analysis where I have a time invariant variable, cross-section variables, and longitudinal variables. The data has 157 firms total with observations for years 2008-2013 for the dependent variable. I included a year and industry dummies in the GEE model without using robust and I got the Wald Chi2 but when I added the robust variance estimate the wald Chi disappeared? Any suggestions?