HI,

So I have panel data for 5 years (4,5,6,7,8) and I am evaluating a policy change that happened just after year 6. So now my pre-policy years are 4 and 5 and post-policy years are 6,7,8. I am trying to categories the individual (id) into pre and post-policy based on when they used a particular service (x, where x is is a dummy variable x=1 if they used the service, zero otherwise) please see the following example

id year x
1 4 1 ( id 1 is a pre- policy user)
1 5 0
1 6 1
2 4 0
2 5 0
2 6 1 ( id 2 is a post policy user)
3 4 1
3 6 1 (id 3 is a pre policy user)
4 4 .
4 7 1 (id 4 is a post policy user)

So if an individual uses the service in all the years they are still considered pre-policy users. They are only considered post-policy users if they use the service only in year 6, 7, or 8

Can anyone help as to how one does that? Thanks for your help in advance


Kind Regards,
Aarushi