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RE: st: Pooling DHS surveys: svyset command?


From   <M.Vandemoortele@lse.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Pooling DHS surveys: svyset command?
Date   Wed, 25 Jul 2012 14:33:51 +0100

Dear Steve,

Thank you for your response.

You are correct - the v024 variable does not designate regions in the
Malawi 2000 DHS. 
Thankfully a statistician who works for MeasureDHS has kindly clarified
the issue:

"I guess it was stratified by urban/rural crossing district defined by a
country specific variable S006. But when you check the frequency, some
urban stratum might have only one cluster selected. If this poses
problems for your application, I suggest you to use V023 crossing V025,
this gives you the best approximation of the stratification.  Hope this
helps." 

Very helpful.

Best,
Milo

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Steve Samuels
Sent: 24 July 2012 15:38
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: Pooling DHS surveys: svyset command?


Milo-

If the information you provide is correct. our -svyset- statement is OK.
However your description of the 2000 sample appears to be inaccurate, as
11 districts were designated for oversampling
(www.measuredhs.com/pubs/pdf/FR123/FR123.pdf). These do not appear to be
"regions", but rather sub-strata of the regions to which they belong. So
I doubt that "v024" designates regions in 2000, but leave it to you to
check. 

Steve
sjsamuels@gmail.com





On Jul 24, 2012, at 9:13 AM, <M.Vandemoortele@lse.ac.uk>
<M.Vandemoortele@lse.ac.uk> wrote:

Dear Stata list serve members,

I am pooling three years of Malawi DHS data (2000, 2004 and 2010). How
would you recommend that I take into account the survey design given psu
and strata variables and adjustment weights? 

The sampling designs differ across surveys and seem to be as follows:
- DHS 2010: stratified by district then urban/rural. Clusters were
selected using probability-proportionate to size (PPS) (frame was the
2008 census enumeration units)
- DHS 2004: stratified by region then urban/rural. Clusters were then
clusters selected using PPS (Frame 1998 census enumeration units)
- DHS 2000: stratified by region then urban/rural. Clusters were
selected through systematic sampling (Frame 1998 census enumeration
units) 

Instructions on the DHS website say do the following: 
- to generate weight: generate weight = v005/1000000
- to make unique strata values depending on how sampling design (in this
case already done for 2010, and 2004 and 2000 v025 and v024 represent
region and urban/rural variables): egen strata = group(v024 v025), label

DHS website, however, does not appear to indicate how to take into
account survey design when surveys are pooled.

On the Stata ListServe the following recommendations are provided on a
related, but non-DHS, question
(http://www.stata.com/statalist/archive/2008-10/msg00521.html):

If your surveys were stratified, to begin with, then it would become: 
svyset psuXyear [pw=weight in each wave], strata(waveXoriginal_strata)

where -X- stands for interaction along the lines of:
egen psuXyear = group(psu year)

Svyset command I use is as follows:
svyset psuXyear [pw=weight], strata(strataXyear) singleunit(scaled)

For pooling DHS surveys, does this svyset command look appropriate?

Best regards,
Milo


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