kmatch port

[maximilian-sprengholz]

Is done so far for use with kmatch and suboptions md, em, and ps -- see test.do; all the programs are part of postestimation.ado

The nopopost wrapper does two things atm:

1. Call a Nopo (2008) style decomposition after matching via kmatch. If nopopost decomp varlist is passed, this wrapper calls a basic cem version of kmatch, otherwise it checks if all requirements are met by the kmatch performed before nopopost. Estimates are returned for the decomposition components and a few auxiliary things.
2. Call postestimation stuff:
   • nopopost gapoverdist: plot gap components over the outcome distribution
   • nopopost dadb varname:plot contributions to DA/DB by variable level
   • nopopost summarize varlist: show summary table by group (A_um, A_m, A_m^B / B_m^A, B_m, B_um)

Open stuff:

• [x] nice SMCL output for decomp and summarize
• [x] your check if variance-covariance matrix is correct: in any case, standard errors are larger after kmatch compared to nopomatch (in the current example sometimes as much as 2x larger); were the bootstrapping standard errors correct?
• [x] some of the proposed options/enhancements might be too much, see my comments in the other tickets

[maximilian-sprengholz]

Moved to nopo.ado. Ready for testing, see test.do.

[maximilian-sprengholz]

Closing in favor of other, more detailed issues.