This is a 8-digit numeric variable with 2 implied decimal places.
SPMWT is the weight variable that should be used to calculate poverty rates using the Supplemental Poverty Measure (SPM). SPMWT differs from the ASEC supplement weight WTSUPP used to estimate official poverty rates. SPM weight is a family based weight and should be used if doing family-level analysis (e.g. % families receiving foodstamps). For individual-level analysis, the ASEC supplement weights should be used.
Estimates on the entire population are prepared by projecting forward the resident population from the last available census. These projections are derived by updating the demographic census data from a number of other data sources that account for death, births and net migration. About 3 years after every census (i.e. 2003 for the 2000 Census and 2013 for the 2010 Census), the Census Bureau updates its independent population control and provides a new weight for the relevant years.
Two important points should be noted here. First, the lag between when the Census is conducted and when the CPS weights are updated is about 3 years. While the Census data are being processed, the CPS files are made available using the weighting scheme from the US Census prior to the latest Census. Second, once the files are updated, the old weights become obsolete and are replaced in the IPUMS data extract system. Published estimates from the lag years that use the old weights are not always updated. For example, 2010 poverty estimates were released in ASEC using the 2000 population controls. Once the 2010 population controls were made available, IPUMS-CPS replaced the ASEC 2010, 2011, and 2012 weights that are based on the 2000 population control with weights that are based on the 2010 population controls.
IPUMS-CPS makes available only the most up-to-date weights.
For more information on calculation of the SPM, see the Census Bureau's "The Research Supplemental Poverty Measure" report.
- All persons.
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