U.S. Census Bureau average 3.13 kids average family size smaller families in North America 2015年の1世帯あたり平均人数 3.14 people in the US in 2015 people per household in the US in 2015 3.14 persons in reality in reality Средний размер семьи в США равен 3,14 человек smaller families in North America average 3.13 kids people per household in the US in 2015 average 3.13 kids average size of a family 3.14 people