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# Re: st: Panel data by subgroups

 From Ken Ning To statalist@hsphsun2.harvard.edu Subject Re: st: Panel data by subgroups Date Fri, 14 Jun 2013 14:59:49 +0100

```Hi Muhammad,

thank you very much for taking the time to reply to me.

The issue is that a company in the last five years might have more
than one case for left_personal_reasons.

The turnover itself is rather a cross sectional event.

If I simply run the regression using dummy variables for the whole
period, those periods that have other reasons for financial managers
turnover events are also used and affect the estimation.

A friend said i should take each group and pool the three year before
the turnover and three year after the turnover together.

e.g.  left_personal_reasons (occured in 2002) so take 1999, 2000, 2001
,(2002) , 2003 , 2004 and 2005.
the next  left_personal_reasons (occured in 2005) so take 2002 , 2003
, 2004 , (2005), 2006, 2007, 2008.

I think this becomes pooled data?

or is there a way to solve this?

many thanks,
Ken

Hello

Either you can create a categorical variable, says its name is
category, which has a value of 1 for promotion, 2 for fired and 3 for
left_personal_reasons, and can run the category specific regressions
like

Before running the regressions you can define another set of three
variables like category1 (having value of 1 if promoted otherwise 0),
category2 (having value of 1 if fired otherwise 0) and category3
(having value of 1 if left_personal_reasons otherwise 0) by using a
-tab- command on the variable containing these categories, assuming.

tab assuming_variable_cateogries, gen(category)

this will create the above defined three variables.

Now you can run the regression for the first case as

xtreg dep_var indep_vars if category==1, (re or fe as required)
xtreg dep_var indep_vars if category==2, (re or fe as required)
xtreg dep_var indep_vars if category==3, (re or fe as required)

or

for the second case

Now you can run the regression for the first case as

xtreg dep_var indep_vars if category1==1, (re or fe as required)
xtreg dep_var indep_vars if category2==1, (re or fe as required)
xtreg dep_var indep_vars if category3==1, (re or fe as required)

This is what I assumed you needed to do. There are other options too to think of

I hope this helps to begin working.

Best of Personal Regards
---------------------------
Assistant Professor/Programme Coordinator
COMSATS Institute of Information Technology
Attock 43600, Pakistan
Learn Econometrics & Stata: elearning.aneconomist.com
http://www.aneconomist.com
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