SPMWT is an 8-digit floating point variable.
999999.0 = NIU (Not in universe)

Description

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 food stamps). 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.

SPM variables prior to 2010 are created by Columbia University's Center on Poverty and Social Research. Details about the methodology used by CPSP to construct the Historical SPM are described in the Historical SPM user note.

For more information on calculation of the SPM, see the Census Bureau's "The Research Supplemental Poverty Measure" report.

Comparability

Prior to 2010, SPM variables are constructed by CPSP using data from the CPS ASEC and other sources to calculate household resources and poverty thresholds. These variables are created using the best possible data available, but some must be imputed due to incomplete data coverage (particularly in the earliest years of the Historical SPM). Users are encouraged to read the Historical SPM documentation for information about CPSP's methodology and use caution when comparing pre- and post-2010 values.

SPMWT is comparable across years from 2010 to 2018.

In 2019, the Census Bureau implemented a new processing system to accommodate survey changes. These changes affect income and relationship variables, making poverty measurements before and after 2019 incomparable. For more information on this overhaul, see our guide to the 2019 ASEC updates.

Universe

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Unharmonized Variables