U.S. Bureau of the Census. April 2012.
The 2010 Census enumerated 308.7 million people in the United States, a 9.7 percent increase from 281.4 million in Census 2000. Of the total population in 2010, 300.8 million lived in 116.7 million households for an average of 2.58 people per household. This was down from an average of 2.59 in 2000 when 273.6 million people lived in 105.5 million households. The remaining 8.0 million people in 2010 lived in group-quarters arrangements such as school dormito-ries, nursing homes, or military barracks. This report presents information on the number and types of living arrangements of American households in 2010 derived from the relationship question on the 2010 Census.
http://www.census.gov/prod/cen2010/briefs/c2010br-14.pdf [PDF format, 21 pages].