Econintersect: According to a U.S. Census report out today (21 June 2012) the number of children aged 18 and older living with their parents in 2010 
was 15.8 million. This was an increase of 1.22 million over 2007.
Some of the other significant numbers reported by the Census Bureau include an increase (2007-2020) in total households by 1.3% but shared households increased by 11.4%, a clear sign of the economic dislocations resulting from The Great Recession.
The following graphic shows that low income is what is driving the participation of those in the shared household situation.
The numbers have been widely misstated in the media. From Housing Wire:
The number of these “adult children” living with their parents grew from 1.2 million to 15.8 million in the three years between 2007 and 2010.
Obviously someone wrote “from” when they meant “by” and no editor picked it up.
Sources:
- Sharing a Household: Household Composition and Economic Well-Being: 2001-2010 (U.S. Census Bureau, June 2012)
- Census Bureau: Shared households increased as economy cratered (Housing Wire, 20 June 2012)
- Census Shows Jump in Shared Households (Daily Real Estate News, RealtorMag, 21 June 2012)
