st: RE: re: 3sls and fixed effects

["Biljana Dlab" <dlab@isb.uzh.ch>]

Thank you very much Kit.

Wish you nice evening.

Best,
Biljana

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Christopher
Baum
Sent: 16 October 2010 21:51
To: statalist@hsphsun2.harvard.edu
Subject: st: re: 3sls and fixed effects

<>
Biljana said

The size is following:

Number of unique values of gvkey_n is  615
Number of records is  6492

I have totally 6492 firm-year observations.

The time period is 30 years (fyears)

That gives me matrix of:

2*((G-1) + (T-1))

2*(614+29)=1286

Is that too large?



I believe it is. You must be running Stata 10.x, as you can't use factor
variables. In Stata 11, -help limits- does not say anything about the
number of variables in an estimation command. I could swear that there
was such a limit in Stata 10 and previous-- I think it was 800. It is
not in the hardcopy manual for Stata 10 (nor 11), and I do not have
access to Stata 10 at present. See what -help limits- on your version 10
system says.

But in any case if you have 615 firm dummies, I suggest you follow my
prior advice and center all of the variables you want to include in the
analysis by firm. Then you don't have to include i.gvkey_n. You can
still include the time dummies, as there are only 30 of them. Centering
both y and the other X variables manually will have the same effect as
including a full set of firm dummies, and should get around the problem
you're encountering.

Kit

Kit Baum   |   Boston College Economics & DIW Berlin   |
http://ideas.repec.org/e/pba1.html
                              An Introduction to Stata Programming  |
http://www.stata-press.com/books/isp.html
   An Introduction to Modern Econometrics Using Stata  |
http://www.stata-press.com/books/imeus.html


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