I’ve been using MARBASECIDP to match IPUMS CPS ASEC and basic monthly records. For years prior to 2016, all or nearly all records in the monthly have a match in ASEC. However for 2016 and 2017, over 6% of monthly records do not appear to have a match in ASEC. Did something change in 2016?
Yes, there was a small change in the 2016 and 2017 ASEC sample design. Specifically, these samples included a split-sample design intended to test new questions regarding health insurance and income. This results in some March basic monthly households not being included in the ASEC sample. A match rate of around 93% is what we expect in these years.