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Re: st: Generate a new variable [four firm concentration ratio]


From   "ALICE DOBSON" <alice_dobson@hotmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Generate a new variable [four firm concentration ratio]
Date   Mon, 21 Nov 2005 18:27:49 -0500

Thanks Nick. It works selectively as I am not getting "firstfour" for all rows.
This is probably because the rows have values for one to seven firms and not for all seven firms
Further, I checked the data editor and see that in such cases where the data is avaiable for less than seven firms the command arranges the top four values s1-s4 (arbitrarily) in columns for say s3-s6
Hence, I do not get firstfour for all such cases
Best,
Alice



From: n j cox <n.j.cox@durham.ac.uk>
Reply-To: statalist@hsphsun2.harvard.edu
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: Generate a new variable [four firm concentration ratio]
Date: Mon, 21 Nov 2005 21:31:19 +0000

If the number of consumers is integer, then
just install -rowsort- from SSC.

rowsort F?_mt, gen(s1-s7) descend
gen firstfour = 100 * (s1 + s2 + s3 + s4) / CONSUM_mt

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

ALICE DOBSON

I use stata 9.1

I have an unbalanced panel data of the type:

geographical region (m = 1..1154)
year (t = 1..7)

with the following variables:

total number of consumers in each region (CONSUM_mt)
total number of consumers of seven firms in each region (F1_mt, F2_mt, F3_mt, F4_mt, F5_mt, F6_mt, F7_mt)


I want to calculate the four firm concentration ratio for each region, C4_mt, which is the proportion of the number of consumers of top four firms to the total number of consumers in that region, in percentage

Could anyone be kind enough to help me with this simple calculation?

GEOGREGN YEAR CONSUM F1 F2 F3 F4 F5 F6 F7 C4
M1 1969
M1 1970
M1 1971
M1 1972
M1 1973
M1 1974
M1 1975
M2 1969
M2 1970
M2 1971
M2 1972
.
.
.
.
.
.
.
.

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