Health Insurance Unit in ACS versus MEPS

The distributions of individuals by HIU size seems to be different between ACS and MEPS: ACS has about 33% one person HIUs and MEPS about 26%. Any guesses as to why? Is there something about the construction of these variables that could explain it?

Specifically I’m looking at the non-institutionalized population, including those age 65+ in counting HIU size but looking at the distribution by HIU size of individuals age 0-64. I’m interested in California / Western region but the basic pattern holds true nationally and at the regional level.


I am not entirely certain how you are identifying HIUs in the IPUMS MEPS data. Perhaps you can provide more information? In the IPUMS USA data, HIUs are identified by SHADAC. Some documentation about how HIUs are defined by SHADAC can be found in this document. A couple additional details to note about this seeming discrepancy. First, the ACS and the MEPS are two independent surveys. They both sample the same population, but end up drawing different people into their samples. This means that even representative statistics will likely be slightly different between these two surveys. Second, both of the figures reported above have an associated margin of error. It might be worthwhile to see if these margins of error overlap, which would indicate that these figures are actually not too far off.
Comparing the documentation of how SHADAC identifies HIUs and comparing it to how you are identifying HIUs in IPUMS MEPS, along with information about the respective margins of error around these estimates, will provide a good understanding whether this seeming discrepancy is relatively large or not. Feel free to follow up with additional details.

HIU is direct from MEPS. Wondering if there’s anyone there who’s worked with both data sets and has run across this?…

and from the MEPS documentation:

“Health Insurance Eligibility Units (HIEUs) are sub-family relationship units constructed to include adults plus those family members who would typically be eligible for coverage under the adults’ private health insurance family plans. To construct the HIEUIDX variable, which links persons into a common HIEU, we begin with the family identification variable CPSFAMID. Working with this family ID, we define HIEUIDX using family relationships as of the end of 2011. Persons missing end-of-year relationship information are assigned to an HIEUIDX using relationship information from the last round in which they provided such information. HIEUs comprise adults, their spouses, and their unmarried natural/adoptive children age 18 and under. We also include children under age 24 who are full-time students (living at home or away from home). Other children who do not live with their natural/adoptive adult parents are placed in an HIEUIDX as follows…”

Ah, okay. Thanks for this additional information. If you look into the specific definitions of HIUs, they are slightly different. The HIEU variable description defines HIUs in IPUMS MEPS and this SHADAC document details the definition used in IPUMS USA.