st: R-sq within in xtivreg, fe

[jypark@email.unc.edu]

Hello,

I am etstimating FE-IV models using 'xtivreg, fe'.  The results from 
several different runs show that R-sq within is ".", which I am not 
quite understanding what it means.  Does that mean FE-IV models do not 
explain any of within variation, or anything else?

Does anyone know of any reference regarding this issue?

Thanks,
Jeongyoung

*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/