st: psmatch2 with the if condition

["Dr. Roberto Mura" <robertomura2@robertomura.com>]

Dear all, I have a cross sections of companies, some listed some private.
I am trying to find a matching private (undiversified) firm for each 
listed one, on the basis of company size. Also, since my dataset is 
cross country, I am trying to control for country and sic code as 
well. To this end, I have created a condition, called condition1 to 
divide the sample into a set of clusters: catenate condition1 =  country sic2
Now, once a match is found, I need Stata to report some accounting 
data for the matched private firm on the same row as the  listed firm.
I have tried to create a "self-fulfilling" nested loop so that I 
don't need to specify beforehand the total number of clusters 
(condition1) and also because the total number of firms changes with 
different clusters (Ncondition1 below).  The problem that I am facing 
is that psmatch2 does not seem to understand the "if" condition.
I have uploaded the dataset (for version 11 and for version 9 of 
Stata) and the do file in my website under 
www.robertomura.com/psmatch2/  if you want to take a look.
Here is what I do:

use "D:\AAA.dta", clear
catenate condition1 =  country sic2
gen quotedcondition1=1 if quotedcompany==1
replace quotedcondition1=0 if quotedcompany==0 & diversification_orig==1
gen quotednumerator=.
gen quoteddenomenator=.
gen privatenumerator=.
gen privatedenominator=.
egen g=group(condition1)
bysort condition1: gen Ncondition1=_N

local j=1
while `j' <=g {
psmatch2 quotedcondition1 if g==`j', pscore(size) noreplacement
replace quotednumerator=fnetincome if _nn==1
replace quoteddenomenator=shareholdersfundsnew if _nn==1
replace privatenumerator=fnetincome if _n1==_id
replace privatedenominator=shareholdersfundsnew if _n1==_id

local i=1
while `i' <Ncondition1 {
replace privatenumerator=fnetincome[_n+`i'] if _n1==_id[_n+`i']
replace privatedenominator=shareholdersfundsnew[_n+`i'] if _n1==_id[_n+`i']
replace privatenumerator=fnetincome[_n-`i'] if _n1==_id[_n-`i']
replace privatedenominator=shareholdersfundsnew[_n-`i'] if _n1==_id[_n-`i']
local i = `i' + 1
}
local j = `j' + 1
}


The problem seems to lie in
psmatch2 quotedcondition1 if g==`j', pscore(size) noreplacement
What seems to be happening is that the matching is done only for the 
first 3 firms of the first cluster and then Stata is mis-assigning 
the _id since the numbers do not follow the clustering but rather, 
Stata is applying the psmatch2 considering the sample as a whole. If, 
for instance, I change the if condition into:
psmatch2 quotedcondition1 if g==1, pscore(size) noreplacement
then Stata is not matching inside the cluster (condition1) but again 
it is treating the sample as a whole. In other words the "if" 
condition does not appear to be used at all by Stata.

I have tried both version of psmatch2. The one available trough SSC 
(version 3.1.5 2may2009) and the more recent one available from 
http://leuven.economists.nl/stata (4.0.1)
I have Stata/MP 11.0 for Windows (64-bit x86-64)  running on XP Pro 
64. I also tried with the older version I had, Stata/SE 9.2 for 
Windows 64-bit x86-64and things don't change.
Thank you all for your kind attention
Kind regards
R



Dr. Roberto Mura, Ph.D.
Assistant Professor of Finance
Program Director for MSc in Finance and Economics
Program Director for MSc in Finance and Business Economics
The Manchester Accounting & Finance Group
Manchester Business School
home page: www.robertomura.com

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