| Re: Why I am getting different total observations when using iweight for tabulating a variable [message #26116 is a reply to message #26098] |
Thu, 09 February 2023 09:11   |
Bridgette-DHS
Messages: 3044
Registered: February 2013
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Senior Member |
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Following is a response from Senior DHS staff member, Tom Pullum:
When Stata sees "pweight", which is the only type of weight you can use with svyset, it normalizes them to have a mean of 1. Stata does not automatically normalize iweights.
I opened the PR file and entered "tab hv024, summarize(shweight)". I see that the mean of shweight in Pujab (hv024=3) is 989497.01, which after division by 1000000 is .98948701. What's relevant is that this mean is NOT 1. Stata, with pweight, will re-scale to 1. With iweight it will NOT re-scale to 1.
So why does the mean of shweight differ from 1 (or 1000000) in each of the states? It's because DHS has normalized shweight in the HR file, not the PR file. I confirmed that by opening the HR file and entering "tab hv024, summarize(shweight)". Sure enough, the mean of shweight is 1000000 in the HR file.
Thus the discrepancy you observe is just due to the way that DHS normalized shweight for households rather than units, and you are using the PR file, with individuals as units, and Stata (with pweight) has re-normalized shweight. Hope this makes sense. Interesting question.
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