Hi. I am studying the impact of law on employment rates. In order to remove the selection bias, I am trying to implement DID after setting a comparison group in the PSM.

I assume that the law was enforced in 2010.

Please check if the following procedure is correct.

Stage 1. The 2009 dependent variable (employment status) is merged horizontally into the 2010 data using the 'merge' command (via the id variable).

Step 2. Get a matched sample using the 'psmatch2' command.

Step 3. I create an interaction variable and perform DID or DDD.

To be honest, I'm not sure how to merge two years(2009 and 2010) data for DID.

Can you provide me with a STATA DO file that combines PSM and DID? (Although I know the 'diff' command for kernel PSM, I want to use various types of matched DIDs).