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Re: st: DiD
From 
 
inggrid <[email protected]> 
To 
 
[email protected] 
Subject 
 
Re: st: DiD 
Date 
 
Tue, 29 Mar 2011 20:25:41 +0800 (SGT) 
Hi Federico,
I only have data in 2000 and 2007. The reform took place in 2005 (before and after).
So, I could not generate year>2004 etc.
I checked my data. As your speculation, treat and post05treat have the same number of 1!
Is there any suggestion how to run a did regression by using two different data points? 
I couldn't use a RD design, since I can't construct a threshold to determine the eligibility.
Many thanks for the help!
Best,
Inggrid
--- On Tue, 3/29/11, [email protected] <[email protected]> wrote:
> From: [email protected] <[email protected]>
> Subject: Re: st: DiD
> To: "inggrid" <[email protected]>
> Cc: [email protected], [email protected]
> Date: Tuesday, March 29, 2011, 7:06 PM
> > gen post05 = year>2000
> > gen treat_post05 = treat*post05
> 
> > note: post05 omitted because of collinearity
> > note: treat_post05 omitted because of collinearity
> 
> May be "post05" has been omitted because it's always equal
> to 1, and treat_post05 because it's always equal to "treat".
> I guess you misspecified the condition of post05 (it
> shouldn't be "year>2000", but "year>2004" or 
> "year>2005"). 
> Federico
> 
      
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