A new report from the Annie E. Casey Foundation's Kids Count initiative finds that more than a million young children under the age of 10 and more than 750,000 children under the age of 5 went uncounted in the 2000 census. Using data from the U.S. Census Bureau's demographic analysis, the report, Why Are Young Children Missed So Often in the Census? (20 pages, PDF), found that children under the age of 5 are missed in the census more than any other age group. Possible explanations include the fact that young children are more likely than adults to live in rental units and to have large, mobile, or complex families — all of which historically have been difficult to count. The report predicts that achieving an accurate count of children in 2010 may be even more difficult than in the past due to the increased number of children living in unusual housing situations and the growing number of racial and ethnic minority households, which historically also have been difficult to count.