st: xtpcse - "no time periods are common to all panels"

[Wayne Sandholtz <wayne.sandholtz@uci.edu>]

Thanks to Kit, Gordon, and Nick for their helpful answers to my question 
about -xtpcse-.  I had assumed that all of the panels included at least 
some common years, but that was not the case.  There may be easier ways 
to check this, but here is how I did it:

* how many panels are present in each year?
tabstat year, by(year) stat(N)
xtset panel_id year
* what is the pattern of missing years?
xtdescribe
by panel_id: gen yrs=_N
tab yrs
sort yrs panel_id year
* visually checking the sorted data, it was easy to see that countries 
with fewer than 12 years of data were the problem
drop if yrs<12
drop yrs

Wayne Sandholtz


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