U.S. Family Structure and Composition
Families are a major focus of the American Community Survey (ACS), conducted each year by the U.S. Census Bureau. A family, as defined by the Census, includes a householder and all the other people in the housing unit related to him or her, by birth, marriage, or adoption.
Not all households are family households. Nonfamily households include those composed of unrelated roommates, or single-person households. In addition, family households may include non-family members who live in the same housing unit.
Unlike the Census—which is an exact count of people and households every ten years—ACS statistics are estimated based on a representative survey sample. Note that the data in this report presents estimated counts of households, not of people.