From Catherine Rampell

Household formation has slowed dramatically since the recession, as cash-strapped families double up and unemployed recent college graduates are unable to leave behind their parents’ couches. To judge just from demographic statistics, more than a million households that should have been formed in the last few years weren’t, according to Mark Zandi of Moody’s Analytics.

The tally of missing households is approximately equal to the country’s current surplus of vacant homes. The implication is that once people start getting jobs again, doubled-up families will peel off and quickly sop up a lot of that excess housing inventory.