This graph shows the number of people per family in the U.S. from 1960 to 2013. The average american family in 2012 consisted of 3.13 persons.
Families in the United States
According to the U.S. Bureau of the Census, a family is a group of two people or more (one of whom is the householder) related by birth, marriage, or adoption and residing together; all such people (including related subfamily members) are considered as members of one family. Unrelated subfamilies are no longer included in the count of families, nor are the members of unrelated subfamilies included in the count of family members.
The number of families is equal to the number of family households, however, the count of family members differs from the count of family household members because family household members include any non-relatives living in the household.
As of 2013, the U.S. Bureau of the Census counted about 81 million families in the United States. The average family consists of 3 persons in 2013, down from 3.7 in the sixties. This is reflected in the decrease of children in family households overall. 1970, about 56 percent of all family households had children under the age of 18 living in the household. This percentage declined to 44 percent in 2011 in a steady downwards trend.
The average size of a family household varies greatly from state to state. The largest average families can be found in the southwest of the U.S., in Utah and California, both with an average size of 3.5 family members. The smallest families can be found in Maine and Vermont, on the northeastern coast of the U.S., with an average size of 2.8 family members.