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Re: st: Covariance matrice.


From   adiallo5@worldbank.org
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Covariance matrice.
Date   Wed, 25 Aug 2004 17:06:01 -0400

You're right, Stas.
I will post later a more detailed example of what I have in mind.
Have a meeting right now.
Best regards.
Amadou.



                                                                                                                                           
                      Stas Kolenikov                                                                                                       
                      <skolenik@email.unc.edu>         To:       statalist@hsphsun2.harvard.edu                                            
                      Sent by:                         cc:                                                                                 
                      owner-statalist@hsphsun2.        Subject:  Re: st: Covariance matrice.                                               
                      harvard.edu                                                                                                          
                                                                                                                                           
                                                                                                                                           
                      08/25/2004 04:50 PM                                                                                                  
                      Please respond to                                                                                                    
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> I have an income variable grouped into 5 categories (Q1 Q2 Q3 Q4 Q5) ie
> from poorest to richest and I want to compute its covariance with the
> following vector:
>
>         |   0.1    |
>         |   0.3    |
>         |   0.5    |
> X =  |   0.7    |
>         |  0.9     |
>
> How to do that into stata?
> I would appreciate any help.

It looks like you are trying to estimate the Gini coefficient. This would
be a quite risky thing to do with the quintile data, I would argue. Kit
Baum posted a solution, but you should keep in mind when you want to
interpret this data that computing such covariance understates the Gini
coefficient quite notably: just draw the Lorenz curve for the data with
five levels of income corresponding to the discrete distribution you are
dealing with.

 ---                                    Stas Kolenikov
 --       Ph.D. student in Statistics at UNC-Chapel Hill
 - http://www.komkon.org/~tacik/  -- Stas.Kolenikov@unc.edu

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