The (Mis)Measurement of Subfamilies in U.S. Census Data

Matthew Schroeder, University of Minnesota

Subfamilies--family units residing in someone else's household--are an important subject of research, but they have proved difficult to measure. This research documents trends in and dynamics of the Census Bureau's identification of subfamilies by comparing them to highly refined and temporally consistent subfamily measures newly available in the Integrated Public Use Microdata Series (IPUMS). I show that the Census Bureau's measurement of subfamilies leads to highly unlikely interpretations of family interrelationships and that these apparent errors have grown worse over time, affecting even the most recent American Community Survey data. Furthermore, errors are particularly high among young adults, nonwhites, and persons without a high school diploma--precisely those populations that subfamily researchers are most interested in. Researchers should strongly consider avoiding the U.S. Census Bureau's subfamily measures and using the IPUMS subfamily measures instead.