st: RE: Match treated to not-treated firms

[Joe Canner <jcanner1@jhmi.edu>]

Laura,

I have some experience with -cem- and it does most of what you want, with the exception of the specific 5:1 ratio.  Specifying the case:control ratio is included in propensity score matching programs; I'm not sure why that is not available for exact matching programs.

 Is there a particular reason that you want a 5:1 ratio instead of using all possible matches (the -cem- default)? The -cem- authors imply that the default method is to be preferred because it uses "maximal information".

All that said, it wouldn't be hard to write such a program: make two data sets one for cases and one for controls, merge them on the matching variables, randomly choose 5 controls for each case, separate the cases and controls again and append them together.  If you decide you want to pursue 5:1 matching and you can't find any user-written programs, let us know if you need some help putting together such a program.

Regards,
Joe Canner
Johns Hopkins University School of Medicine

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Laura-Sophie Henning
Sent: Thursday, March 20, 2014 8:13 AM
To: statalist@hsphsun2.harvard.edu
Subject: st: Match treated to not-treated firms

Dear all,
I want to identify matches for a set of treated firms and am not sure which matching command allows best to incorporate my matching criteria.
My sample includes 300 treated and 25,000 not-treated firms. The binary variable "treated" (either 0 or 1) indicates treatment. The sample spans the years 2000-2011, across all 2-digit SIC codes.
For each treated firm, I would like to find 5 non-treated matches (with replacement). I would want non-treated matches to be in the same year, 2-digit SIC industry, and size quintile (total assets), and to have the smallest possible absolute difference in terms of book-to-market ratio.
I had a look at cem, nmatch and mahapick but did not find a way to account for all these criteria. Can somebody help? Thanks in advance!
Kind regards,
Laura Sophie Henning 		 	   		  
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/faqs/resources/statalist-faq/
*   http://www.ats.ucla.edu/stat/stata/

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/faqs/resources/statalist-faq/
*   http://www.ats.ucla.edu/stat/stata/