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st: xtivreg2 - little questions

From   Susie Enders <>
Subject   st: xtivreg2 - little questions
Date   Sun, 4 Jun 2006 14:12:12 +0100 (BST)


I am working with xtivreg2 and just wanted to clarify
3 little things:

1. Is it OK to specified lagged value(s) of the
dependent vaiable as regressors, as in
xtivreg2 profit l.profit l4.profit ...(other
regressors etc)?

2. xtivreg2 does not allow one to put in time dummies
in order to carry out 2-way fixed effects by
specifying, as one could with OLS. With
xtivreg2 one gets the error message:
i:  operator invalid
But if I generate individual time dummies (tab date,
g(time)) and then put these time dummies into the
specification as (time1-time48), the regression seems
to run OK. However, I wondered whether, since the
programme does not allow the option, this
approach was wrong anyway? I did include time dummies
( in my OLS regression as this seemed to make
sense and some broad comparability between the
specifications would be nice, but perhaps it is
nonsensical for xtivreg2.

3. What criteria should one use for the # of the bw(3)
option, the bandwidth of the HAC (in the case of
robust) covariance estimator, in order to get
estimates robust to autocorrelation? The examples I
saw used 3 or 4, but I was not sure how to choose

I would greatly appreciate any help with these small
but important (for me) questions.


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