What weight should I use in IPUMS-USA?
To obtain representative statistics from the weighted samples, users must apply sample weights. Follow one of the following procedures:
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For person-level analyses using a weighted sample, apply the PERWT variable. PERWT gives the population represented by each individual in the sample; more precision is available in the 1850-1930 samples than in the 1940-onward samples.
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For household-level analyses using a weighted sample, weight the households using the HHWT variable. HHWT gives the number of households in the general population represented by each household in the sample; more precision is available in the 1850-1930 samples than in the 1940-onward samples. If you are using a rectangularized sample, select only one person (e.g., PERNUM = 1) to represent that household.
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For analyses using sample-line variables from 1940 and 1950, apply the SLWT variable. SLWT gives the number of persons in the general population represented by each sample-line person. (For other samples, SLWT contains PERWT, so applying SLWT to other years of data will not alter results for those years.)
Even the unweighted samples have values for HHWT and PERWT, but every record in those samples receives an identical weight. This allows the application of the weight variables in pooled extracts that contain both weighted and unweighted samples. Otherwise, the use of the weights is optional in the unweighted samples.