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Re: st: Concentration Index for Binary Health Variable

From   John Ataguba <>
To   "" <>
Subject   Re: st: Concentration Index for Binary Health Variable
Date   Tue, 30 Oct 2012 15:01:16 +0000 (GMT)

Dear Abekah

Unfortunately, the DASP program ( does not adjust for the use of discrete variables.  Please note also that Erreygers (2009 a, b) has commented on the use/appropriateness of the normalisation suggested by Wagstaff (2005).

An alternative way to obtain the concentration index is outlined in Kakwani et al. (1997).  This is based on what they called the "convenient regression
approach".  The problem with this is that the standard errors are not computed analytically.  

In any of these cases, you still need to compute the concentration index after the normalisation based on either Wagstaff (2005) or Erreygers (2009a).  With the convenient regression, you can simply use the -nlcom- or -lincom- command after the regression.

I hope this helps......


Erreygers, G. (2009a). Correcting the concentration index. Journal of Health Economics, 28, 504-515.
Erreygers, G. (2009b). Correcting the concentration index: a reply to Wagstaff. Journal of Health Economics, 28, 521-524.
Kakwani, N., Wagstaff, A. & van Doorslaer, E. (1997). Socioeconomic inequalities in health: measurement, computation, and statistical inference. Journal of Econometrics, 77, 87-103.

Wagstaff, A. (2005). The bounds of the concentration index when the variable of interest is binary, with an application to immunization inequality. Health Economics, 14, 429-432

> From: Nick Cox <>
>Sent: Tuesday, 30 October 2012, 15:47
>Subject: Re: st: Concentration Index for Binary Health Variable
>By DASP you presumably mean software downloadable from
>You are asked to make clear _where_ user-written software you refer to
>comes from. This is explicit in the FAQ.
>These authors hide their software behind a registration. That's their
>choice. I note as a matter of fact that this differs from the way that
>almost all user-programmers who publish their programs make them
>available, which is by uninhibited download from the Stata Journal
>website, SSC or personal websites.
>The implication seems to me that you should seek support and guidance
>directly from the authors if other users of the software don't answer.
>I wonder how many people will recognise "Wagstaff" as a reference.
>Please see also Statalist FAQ on citation of references.
>On Tue, Oct 30, 2012 at 1:34 PM, Abekah Nkrumah <> wrote:
>> Am using DASP to compute concentration indices with my health variable
>> being binary. My aim is to do cross country comparison. However
>> Wagstaff argues that for a binary variable, a cross country comparison
>> could be problematic because of possible differences in the mean of
>> the health variable for different countries. So his suggestion is for
>> one to normalise the concentration index by dividing through by 1- the
>> mean.
>> I want to find out if that is what the DASP do when you use a binary
>> variable to compute a concentration index or that will have to be done
>> manually afterwards.
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