st: DiD estimation versus fixed effects when T>2

["Riggieri, Alison C" <ariggieri@gatech.edu>]

I am attempting to take panel data (5 years, for all 50 states +DC) and determine a DiD estimation.  I have four different treatment variables, all dummy variables.  

My question is this:  my adviser told me to to run "xtreg y x treatment 2002 2003 2004 2005, fe" to get a DiD estimation, but I'm not sure that is correct.  He told me to just add dummy variables to the fixed effects regression.

Does that compute the DiD estimation or do I have to interact the treatment and the year?  

thanks in advance,

Alison

-- 
PhD Student
School of Public Policy
Georgia Institute of Technology
Atlanta, GA
508-410-1931
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/