Status:Closed    Asked:Jul 20, 2017 - 09:33 PM

What households are grouped in a single strata in IPUMS-International?

I am looking for clarification on the precise nature of "strata" in most of the IPUMS-International samples. From the page on comparability of this variable across samples, "strata" is described as:

"In most samples, the STRATA variable captures implicit geographic stratification and is created by assigning a unique identifier to groups of between 10 and 19 adjacent households within low level."

My confusion is about what this means in the context of IPUMS being, for instance, a 5% sample of all households. Consider a hypothetical sample that contains 5% of all households. The strata variable has 10 households per strata. Does this mean:

A. The data include 5% of households in each strata. In this case, each strata in reality has 200 households, but data users see only 5% (10) of them, presumably selected randomly.

B. The data include all households in each strata, but only 5% of all strata. In this case, there are 10 households per strata, but there are 20 times more strata in reality than we see in the data.

I am confused because the description calls households in the same strata "adjacent," which implies -- to me -- that a strata includes ten contiguous households, rather than 10 households selected out of a contiguous set of 200.

Does anyone have any insight into this question? It is probably not important for most uses, but it is critical for my purposes.

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Staff Answer


Jeff Bloem


All IPUMS International samples are stratified. This means the population is divided into strata based on geography or other key characteristics. Then, a sample is drawn from each stratum. So, this aligns most closely with case A in your question. More information about sampling design in IPUMS International can be found via this page.

I hope this helps. Let us know if you have any additional questions.


Jul 21, 2017 - 12:01 PM

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