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st: RE: Keep subsequent observations in panel data


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Keep subsequent observations in panel data
Date   Mon, 5 Oct 2009 15:36:13 +0100

What about individuals who do not appear in the first wave? What do you
want to do with them? 

Nick 
n.j.cox@durham.ac.uk 

Nikolaos Kanellopoulos

I have a very simple unbalanced panel, where individuals are allowed to
drop in and out of the sample. I want to create two separate datasets
with  the following sampling criteria.

For the first one, individuals  that appear in the first wave should
remain in the sample at subsequent years until the first time they drop
out of the panel,
either completely or not. If they rejoin the panel later these
observations should not be used. For instance in the following example I
want to keep only observations 129 and 130.

+----------------------+
i   t   y 
----------------------
129.  1      1     0 
130.  1      2     0 
133.  1      5     0 
134.  1      6     0 
135.  1      7     0 
136.  1      8     0 
+----------------------+
137.  2      2     0 
138.  2      5     0 
139.  2      6     0 
140.  2      7     0 
141.  2      8     0 
+----------------------+

For the second dataset individuals should remain in the sample at
subsequent years from the first time they are observed until the first
time they drop out of the panel, either completely or return again.
Again , if they rejoin the panel later these observations should not be
used. For instance in the following example I want to keep only
observations 129 to 130 and 137.

+----------------------+
i   t   y 
----------------------
129.  1      1     0 
130.  1      2     0 
133.  1      5     0 
134.  1      6     0 
135.  1      7     0 
136.  1      8     0 
+----------------------+
137.  2      2     0 
138.  2      5     0 
139.  2      6     0 
140.  2      7     0 
141.  2      8     0 
+----------------------+


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