I’ve been digging into the spm geographic adjustments, and I’ve noted that the base geographic adjustments reported by Fox (2018) for 2017 – in the table " SPM Thresholds by Metro Area" https://www.census.gov/library/publications/2018/demo/p60-265.html, and also in the underlying research data set (variable spmu_geoadj) do not match the base thresholds in the IPUMS CPS data set (spmgeoadj) for specific geographic areas (e.g., Oregon metro, Oregon nonmetro). There are seven spmgeoadj values for the base threshold of each housing tenure type in both data sets, but that don’t match, which doesn’t make sense to me, since they should be based on the same underlying variables (index of median gross rents, share of threshold devoted to shelter and utilities, and BLS FCSU thresholds for each tenure group).
Can you explain why this is the case? Did IPUMS use a different underlying median gross rents index and/or share of threshold for the various housing tenure groups? Do I need to worry about this?