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st: RE: RE: lagging variables in 3-dim unbalanced panel w/ gaps


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: RE: lagging variables in 3-dim unbalanced panel w/ gaps
Date   Fri, 21 Jun 2002 08:38:39 +0100

helen milner
> 
> I am trying to find a way to lag variables in a 3 dimensional panel
> dataset.  I have 25 countries each with unique election dates from
> 1945-98 (day-month-year in stata format) and each with political
> parties. On average, each party has gone thru 15 elections, and I want
> to use a party's score from the last election to predict something about
> the way it behaves in the current election. 
> The problem seems to be that the election dates are unique to each
> country and have gaps within them (i.e., US presidential elections occur
> every four years). When I try to use the L1 command after tsset-ing the
> data ("tsset pty edate"), Stata creates a variable with 0 observations.
> I have been doing the lagging manually, but that is cumbersome and
> error-prone. Is there some way to get Stata(v7) to lag the variables?
 
It sounds as if there is an easy solution to part of this: 

If you create a variable from 1 up 

bysort pty (edate): gen eorder = _n 

You can then 

tsset pty eorder 

In other words, the natural metric is election number, not years. 

Are you intending that each party can be modelled 
as a separate time series, without reference to 
other parties in the same election? 

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