In 2007, 16 percent of all U.S. residents 18 and older were living in situations in which they were neither the householder, or the householder's spouse or partner. Last year, 17.9 percent of all adults were in that situation.
More than half of those in shared households last year were adult children, and most of the rest were relatives. Fewer than one in five were non-relatives.
The number of shared households rose from 19.8 million or 17.6 percent of households in 2007, before the economy slumped, to 22.2 million or 19.4 percent in 2010. The number dipped in 2011 to 22 million or 19.2 percent.
In five states, California, Florida, Hawaii, New York and Nevada, and in the District of Columbia more than one in five adults was living in someone else's household in 2011.
Census said sharing a household protected many people from poverty. While 15.8 percent of adults living in others' households had incomes below the poverty line in 2011 based on household income, 55.5 would have been considered poor if living alone.