I linked ASEC 2023 and March 2023 with ‘cpsidp’ but now I’m not sure which is the appropriate weight to use. This scenario isn’t covered by ‘Longitudinal Weight Variables’ (https://cps.ipums.org/cps/cps_linking_documentation.shtml#linked_weights).
Can I still use ASECWT?
The ASEC is a supplement to the March Basic Monthly Survey (BMS) that includes additional (oversample) respondents and questions that are not present in the March BMS. The supplement questions are fielded to all March BMS as well as oversample respondents, and oversample respondents are also administered the March BMS questionnaire. The ASEC sample file appends the new person/household records to the BMS and merges variables from each questionnaire onto a single record. As a result, the March BMS sample is a strict subset of the corresponding year’s ASEC sample on IPUMS CPS. Not only is it unnecessary to download extracts that contain both ASEC and March BMS data, but doing so will artificially inflate estimates as most person records (those not part of the oversample) will be included twice. This is the case for all CPS supplement data obtained through IPUMS CPS.
Regarding weights, person-level analyses of ASEC samples should use ASECWT, while person-level analysis of BMS data should use WTFINL. Analyses that use variables from both the BMS and a CPS supplement (such as the ASEC) should use the supplement’s weight since this corresponds to the stricter of the sample universes. Analyses of Outgoing Rotation Group variables should be weighted using EARNWT. Longitudinal weights should be used when linking records between multiple different months/years of the CPS. IPUMS provides both pre-constructed longitudinal weights (e.g., LNKFW1YWT for weighting linked ASEC samples from adjacent years) as well as guidance on weighting and sample code for creating your own longitudinal weights using iterative proportional fitting.