Re: st: xtile creating different deciles using same data

[johnataguba@yahoo.co.uk]

-----Original Message-----
From: Nick Cox <njcoxstata@gmail.com>
Sender: owner-statalist@hsphsun2.harvard.edu
Date: Tue, 3 Jan 2012 12:59:40 
To: statalist@hsphsun2.harvard.edu<statalist@hsphsun2.harvard.edu>
Reply-To: statalist@hsphsun2.harvard.edu
Subject: Re: st: xtile creating different deciles using same data

So it seems possible that different samples are picking different  
weights even for the same household income and as a consequence - 
xtile- will yield different results.....

Nick

On 3 Jan 2012, at 12:43, "Alvaro Herrera E."  
<A.N.Herrera@sussex.ac.uk> wrote:

> Just checked, and it isn´t.
>
> best,
>
> Alvaro.
>
>
> On 2 January 2012 22:01, Nick Cox <njcoxstata@gmail.com> wrote:
>> Back to the Stata question:
>>
>> Is -weight- also constant within households?
>>
>> Nick
>>
>> On Mon, Jan 2, 2012 at 8:23 PM, Cameron McIntosh  
>> <cnm100@hotmail.com> wrote:
>>
>>> A comment on the nature of your income variable, as this is not a  
>>> trivial matter. Per capita income is indeed preferable to raw  
>>> total household income but is still not optimal, for reasons  
>>> discussed in:
>>> Carson, J. (2002). Family spending power. Perspectives on Labour  
>>> and Income, 3(10), 24-32.http://www.statcan.gc.ca/studies-etudes/75-001/archive/e-pdf/5018698-eng.pdf
>>>
>>> I would suggest weighting in the manner Carson suggests (or  
>>> slightly differently if the context warrants), and see if this has  
>>> an impact on the results.  Perhaps some of the OECD measures might  
>>> be useful as well:
>>>
>>> http://www.oecd.org/document/51/0,3746,en_2649_33933_49147827_1_1_1_1,00.html
>>
>> From: A.N.Herrera@sussex.ac.uk
>>
>>>> Hi, I am using the command xtile on stata 11, 32bits, to create  
>>>> income
>>>> deciles on my database, but I found an inconsistency:
>>>>
>>>>
>>>> I have a variable with the household per capita income, with data  
>>>> for the
>>>> whole population. Then I create deciles, but I don't do it over the
>>>> population, but households.
>>>>
>>>> To do so, I use only one observation per household (they all  
>>>> share the
>>>> same household per capita income) to create my deciles, and then  
>>>> I assign
>>>> the rest of the household members to the decile of such  
>>>> observations.
>>>> Of course, as poorer families tend to be larger, I end up with  
>>>> deciles that
>>>> have more than 10% of the population on the lower end of the  
>>>> distribution,
>>>> and others with less than 10% on the other end. That's fine with  
>>>> me.
>>>>
>>>> basically, what I do is
>>>> xtile decaux==income if count==1 [w=weight], nq(10)       where
>>>> count==1 is the first member-chosen randomly- of each household,  
>>>> and
>>>> then
>>>> recode decaux .=0
>>>> by id_househ: egen decile=sum(decaux)                          I
>>>> assign the other members of each household to the deciles of their
>>>> respective members (count==1)
>>>>
>>>>
>>>> The problem is that  if I run the same commands on the same  
>>>> database for a
>>>> second time (or a third, or fourth, always without modifying the  
>>>> data),
>>>> then the number of observations assigned to each decile differs  
>>>> every time.
>>>>
>>>> The overall population does not change, but the population  
>>>> assigned to the
>>>> deciles changes marginally every time.
>>

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