Hello together,

I have a paneldata set and I want to run propensity score matching and restrict/force matching on region in order to ensure that firms only become matched if they are located in countries that have a comparable score for the control variables (Treatment independent). But Stata gives me the following error:

Code:
. teffects psmatch (Inno) (dum_ICT firmage l1 c3 c6 a4a a1, probit) if a1==27&10
there is only one level in treatment variable dum_ICT; this is not allowed
r(459);
I would really appreciate if one of you experts can help me. Thank you very much!

Kind regards
Dominik