Hi Casey, Matching on the outcome is certainly problematic....imagine if you got perfect balance (which you would hope to do), then that would also imply a 0 treatment effect! What wouldn't be problematic (and in fact would be good) is if they were actually matching on a pre-treatment measure of the outcome. E.g., in education studies there is often pre-treatment test scores available, where those same tests form the outcome value as well (but then measured post-treatment). This kind of matching on the outcome variables (but measured before the treatment) can be very effective. Thanks Liz On 7/27/09 2:56 PM, "Casey Klofstad" <klofstad(a)gmail.com> wrote: Hey all- In a paper I'm reviewing one of the covariates used in a 1-to-1 matching procedure ends up also being used as the dependent variable in the final analysis. From a theoretical point of view this seems odd, since the variable is being treated as both a pre- and post-treatment variable. But, is there any empirical reason to be worried about this? Thanks much, -c -- Casey A. Klofstad University of Miami Department of Political Science Coral Gables, FL klofstad(a)gmail.com http://www.as.miami.edu/personal/cklofstad/ -- MatchIt mailing list served by Harvard-MIT Data Center List Address: matchit(a)lists.gking.harvard.edu Subscribe/Unsubscribe: http://lists.gking.harvard.edu/?info=matchit MatchIt Software and Documentation: http://gking.harvard.edu/matchit/ Browse/Search List Archive: http://lists.hmdc.harvard.edu/lists/matchit/