The Net Undercount of Young Children in the Census: 1950-2010

William O'Hare, Independent Consultant

Despite evidence that children under age 5 have relatively high net undercount rates in the U.S. Census, this issue has received very little attention among demographers. This study starts to address that gap by providing data on the undercount of young children in the 2010 U.S. Decennial Census and comparing the results of the 2010 Census to the results of earlier Censuses. In 2010, young children have a net undercount rate of 4.6 percent which is higher than any other age group. In 2010 there was a net undercount of almost one million persons under age 5. The net undercount rate for young children fell from 1950 to 1980, but since 1980 the net undercount rate for young children has increased consistently and substantially while that for adults has continued to decline.