In a generalized Difference in Difference for staggered year event, from this discussion, we need to include the event year to the sample.
For example, if Korea passed the law in 1997, so post*treat should receive the value of 0 for 1995 and 1996 while it receives the value of 1 for 1997,1998,1999,2000,2001,2002.
I am wondering if I can exclude the year 1997 in this case out of my sample, is there any justification for this exclusion. I mean, post*treat equals to 0 for 1995 and 1996 while it receives value of 1 for 1998,1999,2000,2001,2002.
If this exclusion is wrong, so I am wondering why it is wrong.