The Pew study, out Thursday, says a record 21.6 million young adults between 18 and 31-years old are at home with mom and dad. That's 36 percent of the age group, the highest share to live at home in at least 40 years, Pew says.
The study points to a number of likely causes, including both rising college enrollment and falling employment for young adults.
Some 32 percent lived with their parents before the Great Recession hit in late 2007.
Many of them are likely college students. The census counts students living in college dormitories as living with their parents.