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Re: st: Demeaning TFP


From   SAM MCCAW <sam2stata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Demeaning TFP
Date   Wed, 10 Oct 2012 18:01:17 -0400

Also, would it be better just to center lnTFP by using:

     bys country_no industry_no: center lnTFP, gen (lnTFP_pooled_centered) ?

Thanks again.


On Wed, Oct 10, 2012 at 5:53 PM, SAM MCCAW <sam2stata@gmail.com> wrote:
> Dear All,
>
> I am trying to assess productivity spillovers from foreign to domestic
> firms and am using levpet as my productivity estimation technique.
>
> After I run levpet (both on pooled sample and then industry by
> industry) I get some gigantic values for lnTFP.
>
> My sample for running levpet includes both domestic and foreign firms,
> i.e. I am not running levpet for domestic firms only.
>
> The summary stats for lnTFP are as follows:
>
>     Variable |             Obs        Mean    Std. Dev.       Min        Max
> -------------+--------------------------------------------------------
> lnTFP_pooled   |     21923   -1247.003    106482.5  -1.43e+07   17.18935
> lnTFP_industry |     18710    -5587274    3.56e+08  -4.57e+10   24.17001
>
> Now I would like to demean TFP but since I have so many really high
> negative values, would demeaning lnTFP by country and industry just
> make it worse?
>
> Also, I am afraid to restrict the sample to a certain level of lnTFP,
> for example as far as - 100.
>
> Preferably I would just restrict the sample to exclude outliers but I
> have about 3000 firms which have lnTFP less than -50 in a total sample
> of 21923.
>
> Also, if I go ahead and use these lnTFP values in my regression, by
> elasticity magnitudes turn up to be 4 digits long. Yikes.
>
> I have tried data transformations and so on but am at a loss. Any
> thoughts would be greatly appreciated.
>
> Thanks.
>
> SAM
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