# Difference-in-differences Matching

I have a difference-in-differences analysis. My treatment is at the county level. Each county received the treatment at a certain point in time.

I want to proceed with a propensity score matching as an extension to get DiD-matching results . I know everything about PSM, however, I am not quite sure how to get the STATA command in order to:

1. Generate Pre- and Post-treatment dummies since I don't have a treatment at one point in time; i.e. DD is staggered.
2. Use the DD with pscore
• What is the name of the time variable, and what range of values does it take on? Which year or month is the treatment done in? – ahorn Apr 25 '19 at 15:22

You can use mark. For example, if the treatment was done in the year 2000, and your time variable is called time, the syntax is
mark treatment if time >= 2000 & time <.
where treatment is the dummy that is generated.