Re: st: using svyset with pooled cross-sections from IPUMS-CPS

[Stas Kolenikov <skolenik@gmail.com>]

Patrick Lapid is setting up his CPS data for survey estimation, and
provided his -svyset- index and description of the design as follows:

On Tue, Apr 26, 2011 at 11:56 AM, Patrick Lapid <patrick.lapid@gmail.com> wrote:
> I'm currently working on a labor economics project using the U.S. Current
> Population Survey from 2006 to 2010, with the data downloaded from IPUMS.
> I'm concerned if I've declared the survey design correctly. I am attempting to
> analyze the data as pooled cross-sections, using survey estimation. I used
> the following Statalist post as a guide:
>
> http://www.stata.com/statalist/archive/2008-10/msg00521.html
>
> I have the following lines of code to declare the survey design:
>
> . egen hhXyear = group(serial year)
> . svyset hhXyear [pweight=perwt], strata(year)
>
> Since the original clusters (PSUs) were households, indexed by serial number,
> I used egen to create new clusters of households in a given year. I then used
> svyset to set the following:
>
> -clusters (PSUs): hhXyear
> -strata: year (each separate year of the CPS)
> -sampling weight: perwt (person weight, provided by IPUMS)

I don't think this is right. CPS is a rotating design, with the same
households appearing (say) in February, March, April and May in both
(say) 2010 and 2011. With your -svyset-, they would be treated as if
they belonged to separate strata, which is not right (and
counterproductive, actually: this design is optimized to have small
standard errors on the measures of change, with 3/4 overlap between
consecutive months, and 1/2 overlap between consecutive years, which
helps bring down the variances by probably 20% and 10%, respectively,
off the top of my survey statistician's intuition).

-- 
Stas Kolenikov, also found at http://stas.kolenikov.name
Small print: I use this email account for mailing lists only.
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