Dear reader,

Currently I am doing a research for my masterthesis, whereby I use propensity score matching.

However, I have firms that in year 1 are not treated and in year 2 or 3 are treated.
If I perform propensity score matching, I think they will match the same firms that are not treated in year 1 with themselves in the years they are treated.
I've added fiscal year as independent variables, but still the region of common support is .99896195 which is pretty high in my opinion.

Does anyone has a solution for this problem?

Thank you in advance,

Britta Schijff