> Jenny Montaldo wrote:
>
> [...]
>
> > Another related question concern the estimates for white collars. The xtreg, fe have an
> > overall r^2 of 0.27 (much better than the previous one). However when I try the areg
> > command it says that the matrix is not positive definite (I use also some lagged values of > my variable of interests in the estimation).
>
> If your T is small, you should be aware that using lagged dependent
> variables in a fixed-effects model generates biased parameter
> estimates. See Judson and Owen (1999) for more on this.
>
> If you insist in using LDVs in this situation, then you may have to go
> the IV route, after which things can get quite messy.
>
> --
> Clive Nicholas
>
> [Please DO NOT mail me personally here, but at
> <[email protected]>. Thanks!]
>
> Judson RA and Owen AL (1999) "Estimating Dynamic Panel Data Models: A
> Guide For Macroeconomists", Economics Letters 65(1): 9-15.
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