Using categorical variable or year variable as matching variables for psmatch2

[Olivia Johns]

I have a large cross-sectional dataset. I want to estimate the effect of the main variable "treatment" on the outcome Y.
I am using age, income, credit score as matching variables. But i also want to include the variable "year" and a categorical variable "C" since i think these are very important our my treatment as well as my outcome variable Y.

Is it ok to include a categorical variable and a year variable in psmatch2?

I am using probit y x1, x2, ...., i.year, i.cateogory, vce(...).

[David Radwin]

I don't see why not. But yours is a substantive question, not a Stata or psmatch2 question. Also, if you are using probit just to calculate propensity scores, it doesn't matter if you specify an alternate type of variance estimation in vce() because propensity scores are based only on the estimates.

Finally, as requested by FAQ 12.1, "If you are using community-contributed (also known as user-written) commands, explain that and say where they came from: the Stata Journal, SSC, or other archives." psmatch2 is by Leuven and Sianesi and is available from SSC.

. ssc describe psmatch2

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package psmatch2 from http://fmwww.bc.edu/repec/bocode/p
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TITLE
      'PSMATCH2': module to perform full Mahalanobis and propensity score matching, common support graphing, and
        covariate imbalance testing

DESCRIPTION/AUTHOR(S)
      
      psmatch2 implements full Mahalanobis and propensity score
      matching, common support graphing, and covariate imbalance
      testing. This routine supersedes the previous 'psmatch' routine
      of B. Sianesi. The April 2012 revision of pstest changes the
      syntax of that command.
      
      KW: propensity score
      KW: matching
      KW: treatment
      
      Requires: Stata version 11
      
      
      Author: Edwin Leuven, Ecole Nationale de la Statistique et Administration Economique (ENSAE)
      Support: email [email protected]
      
      Author: Barbara Sianesi, Institute for Fiscal Studies
      Support: email [email protected]
      
      Distribution-Date: 20180201
      

INSTALLATION FILES                             (type net install psmatch2)
      psmatch2.ado
      psmatch2.sthlp
      psmatch2.dlg
      pstest.ado
      pstest2.ado
      pstest.sthlp
      ../d/density2.ado
      psgraph.ado
      psgraph.sthlp
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(type ssc install psmatch2 to install)