The Census Bureau acknowledges the historical undercount of young children in decennial censuses and Census Bureau surveys. Demographers have documented the high undercount of children under the age of five (e.g., Robinson et al 1993, O’Hare 1999, West & Robinson 1999, O’Hare 2009). This is not a phenomenon unique to the U.S. as China, South Africa, Laos, the former Soviet Union, and Canada also experience this high net undercount of young children (Anderson & Silver 1985, Anderson 2004, Statistics Canada 2004 and 2010, Goodkind 2011). Evaluations show that Census Bureau surveys like the American Community Survey (ACS), the Current Population Survey (CPS), and the Survey of Income and Program Participation also undercount young children, which can result in biased survey estimates. In addition, these surveys will never fully correct for this undercoverage, given the use of decennial census counts with known undercoverage as inputs to final survey controls.

The 2010 Demographic Analysis estimated an undercount of almost 1 million children, aged 0 to 4 (about 4.6 percent). O’Hare (2012) found that the net undercount rates for young children in the U.S. Decennial Census increased from 1.4 percent in 1980 to 4.6 percent in 2010, while the net undercount rate for the adult population (age 18+) went from an undercount of 1.4 percent in 1980 to an overcount of 0.7 percent in 2010. The rapid rise in the undercount of young children underscores the importance of examining this population in more detail.

In 2014, the Census Bureau released a task force report summarizing this critical coverage issue and recommending research that the Bureau should consider to better understand the possible causes for this undercount (U.S. Census Bureau 2014b). An interdivisional team is currently working on several projects to investigate the undercount of young children in the 2010 Decennial Census. One of these projects explores the coverage of young mothers to determine if the census might miss young children along with their young mothers. This evaluation report summarizes the results of that investigation.