I am new to Statalist. I am working on my PhD dissertation in
Economics at George Washington University. I would like to use
xtabond2 to estimate an Euler Investment Equation using the GMM system
estimator.
I leaned about xtabond2 from the internet while looking for some
Econometric papers (as it is not part of STATA 8.0 which I am
currently using).
My dissertation advisor is asking me if this command "xtabond2" has
been validated or authorized ?.
In private correspondence, I suggested that Dahlia contact xtabond2
author David Roodman (who is also located in DC), and that the xtabond2
help file contains several examples that allow you to generate the same
results (using the same data) as does Doornik's DPD for Ox. In that
sense I consider that the xtabond2 routine is validated, in that the
author has provided benchmarks for which his routine matches DPD for Ox
(except for one issue, where Roodman believes that Doornik;s code is
off by a factor of two on a particular stat: still an unsolved
mystery). The validation of xtabond2 against alternative software
exceeds the level of validation commonly provided for user-contributed
Stata code IMHO.
As for the notion of "authorized", it is not relevant for
user-contributed code in the Stata user community. No one is able to
authorize or deauthorize user-written routines. As I have stated before
on this list, if users raise issues with a particular routine, and the
author(s) of that routine do not respond to enquires or bug reports (or
are no longer involved with developing the code), then I will withdraw
the routine from the SSC archive. That does not prevent software from
being distributed, as any user may make Stata routines available from
their own pages. But inclusion of a routine in SSC does not provide any
assurance that it does what it is supposed to do. That is the
author(s)' assertion, not mine, and users of the software do so at
their own risk. But then that is true even for commercial software, is
it not? A couple of long-lived bugs in Excel functions come to mind...
