Omitted "Treatment" variable in DiD fixed panel regression

01 May 2021, 08:30
Hi, I'm currently studying the effects of mandatory CSR disclosure on firm performance. My data set consists of firm-year variables from 27 EU countries from 2011 to 2018. I generate variable "Post" if the year is greater than 2014.
My treatment group is firms in countries with non-compliance penalties. It is actually based on country, not firm. So, my regression command is as follows:

xtreg ROA_NI_w post treatment post_treat size cash fd gr i.SICcode i.year, fe

(I didn't add i.country since "treatment" is based on the country. If this is wrong, please let me know.)

and I got results as below:

Fixed-effects (within) regression Number of obs = 8,285
Group variable: compid Number of groups = 1,187

R-sq: Obs per group:
within = 0.0374 min = 2
between = 0.1029 avg = 7.0
overall = 0.0460 max = 7

F(11,7087) = 25.04
corr(u_i, Xb) = 0.1048 Prob > F = 0.0000

------------------------------------------------------------------------------
ROA_NI_w | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
post | .27638 .4879204 0.57 0.571 -.6800898 1.23285
treatment | 0 (omitted)
post_treat | -.4764226 .4547777 -1.05 0.295 -1.367923 .4150775
size | 4.360291 .3508205 12.43 0.000 3.672578 5.048004
cash | 9.076161 1.061664 8.55 0.000 6.994982 11.15734
fd | .8019895 3.059513 0.26 0.793 -5.195571 6.79955
gr | 19.24324 4.655786 4.13 0.000 10.11651 28.36997
(For the rest of results, they are omitted to save the space.)

I don't know why "treatment" is omitted. When I excluded i.country, the "treatment"" omitted as well. I don't know what should I do for solving this issue?
I attach pictures of my dataset. Thank you in advance.