Dear Stata community,

Hi, I have a panel data (Company ID, years) independent variables(MTB, size, growth, roa, tangibility, covid19: dummy), and dependent variable (leverage).

I tried to rung a command: xtreg leverage MTB size growth roa tangibility covid if year == 2016, fe
However, Stata drops every independent variable due to collinearity even though the only added dummy is covid variable.
So I took covid out and re-run the command but Stata still drops all variables due to the same reason.
So, I ran the command without if: xtreg leverage MTB size growth roa tangibility covid, fe
It perfectly runs fine.

However, I would like to run xtreg command for each year(from 2016 to 2021), is there any possible solution for this?

P.S: I dropped every independent variable by one but it still suffered from collinearity, so I believe it is a matter of year variable.

Any advice is appreciated!

Thanks in advance

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