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Re: st: Decile regression using sqreg


From   Maarten buis <maartenbuis@yahoo.co.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Decile regression using sqreg
Date   Fri, 25 Apr 2008 16:29:36 +0100 (BST)

--- Leonor Saravia <lmisaravia@gmail.com> wrote:
> I understood that I'm having a problem with the interpretation of
> the coefficients, because I can't understand what's the meaning of
> each one of the coefficients obtained with this command.
> 
> I'm working with some households surveys for latinamerican countries,
> so the data I'm using has the next variables:
> 
> household_identifier     income    food_expenditure
> 123                               1000         800
> 445                                2980        1500
> 670                               500            250
> .                                     .                 .
> .                                     .                 .
> .                                     .                 .
> 870                              15200          14000
> 
> 
> The model that I'd like to perform is this:
> 
> income = a + b*(food_expenditure) + error
> 
> And I need to compare the coefficients for each decil of income of
> the population of each country, something like comparing the
> coefficient for the food expenditure done by 10% of the poorest
> population and the richest 10% of the population.
> 
> I think that the quantile regression is the way to do this, using the
> "sqreg" command, am I wrong?
> 
> That's why I thought that I need 10 regressions instead of 9, because
> I need to compare the coefficients for each one of the 10th parts of
> the population.

In your model you are thinking that food expenditure causes income, I
would say that it is the other way round. 

Anyhow, you are probably looking for something like this:

*-------- begin example ------------
sysuse nlsw88, clear
drop if missing(grade)
egen decile = cut(wage), group(10) 
tabstat grade, by(decile) s(mean)
*--------- end example -------------
(For more on how to use examples I sent to the Statalist, see
http://home.fsw.vu.nl/m.buis/stata/exampleFAQ.html )

Here you see the mean grade (in your case food expenditure) for the 10%
poorest (coded 0), between 10-20% poorest (coded 1), etc.

Hope this helps,
Maarten

-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands

visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434

+31 20 5986715

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


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