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st: re: Group building according to given report dates and company


From   Kit Baum <Baum@bc.edu>
To   statalist@hsphsun2.harvard.edu
Subject   st: re: Group building according to given report dates and company
Date   Sat, 21 Mar 2009 15:55:12 -0400

<>
This should be much easier to handle in long format, which gets away from all the issues about how many reports there are per company.

------------
clear
input company year
1 1939
1 1945
1 1952
2 1938
2 1941
2 1946
2 1953
3 1937
3 1940
3 1948
3 1954
end
sort company year
save reptdates, replace
webuse grunfeld, clear
drop if company > 3
keep company year invest
merge company year using reptdates, uniqusing
g reptyear = (_merge == 3)
drop _merge
// transform reptyear to indicate the report period for each company
bys company: replace reptyear = sum(reptyear)
// calculate the sum of a firm-level variable over each report period
bys company reptyear: g cuminv = sum(invest)
bys company reptyear: g lastyear = _n == _N
l company year reptyear cuminv if lastyear, sepby(company)
--------------------


Kit Baum   |   Boston College Economics and DIW Berlin   |   http://ideas.repec.org/e/pba1.html
An Introduction to Stata Programming   |   http://www.stata-press.com/books/isp.html
An Introduction to Modern Econometrics Using Stata   |   http://www.stata-press.com/books/imeus.html



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