Despite its enormous size, the millennial generation has not had the impact on the US housing market that we would normally expect. One big reason for that is more young adults are living with their parents, or other relatives, than at any time since 1940. From the Wall Street Journal:
Despite a rebounding economy and recent job growth, the share of those between the ages of 18 and 34 doubling up with parents or other family members has been rising since 2005. Back then, before the start of the last recession, roughly one out of three were living with family.
The trend runs counter to that of previous economic cycles, when after a recession-related spike, the number of younger Americans living with relatives declined as the economy improved.