State Undercount Rates for Young Children in the 2020 Census

Dr. William P. O'Hare

Over the past decade there has been growing interest among researchers and Census stakeholders in the high and growing net undercount of young children (ages 0 to 4) in the U.S. Census which has resulted in a stream of research on this topic (O’Hare 2015: U.S. Census Bureau 2022;  Jensen 2022; Griffin and O’Hare 2022).  This paper extends that stream of research by providing newly available estimates of state net undercounts for ages 0 to 4 in the 2020 Census.

The undercount estimates used here are derived by comparing the Census counts to the Vintage 2020 Population Estimates. The population estimates are thought to be more accurate than the Census for two main reasons.  First, there is clearly a high net undercount of young children in the 2020 Census.  Second, the population estimates for ages 0 to 4 are largely based on birth certificate data which is widely  thought to be very reliable.  The Census Bureau’s 2020 Demographic Analysis tables show 99 percent of the population ages 0 to 4 are accounted for by births (U.S. Census Bureau 2020). This method has also been used by other researchers (O’Hare, 2014; Jensen and Johnson 2022; King  et al. 2018; Hartley et. al. 2021).