Why do so many Millennials live with their parents? Two theories: marriage and debt.

To put it another way, when it comes to twenty- and thirtysomethings living with Mom and Dad, it’s possible we’re looking at something close to a new normal.
http://www.slate.com/blogs/moneybox/2015/02/10/millennials_living_with_parents_it_s_harder_to_explain_why_young_adults.html