Dear Stata community,

I am running ec2sls model: xtivreg investment ( bribery = elf (time invariant instrument) ) hdi pop_growth educ_expenditures i.year , first re ec2sls
After that I would like to get F-statistics for excluded instruments. I run xtoverid, noi and get the following message: Warning - endogenous variable(s) collinear with instruments
Vars now exogenous: __000018 __00001B __00001E __00001H __00001K
Warning - collinearities detected
Vars dropped: __00001I __00001J __00000W __00000Z __000012 __000015
As I realized one of the dropped variables were my instruments and I can't get the F statistics for them. When I don't include year dummies in my model I don't get this message. Could you please give me an advice what is wrong with my model and how I could solve the problem?