A record 21.6 million young adults lived in their parents’ home in 2012, according to a new study from Pew Research.

Fully 36 percent of the Millenial generation – people aged 18-31 — were living with their folks, the highest ratio in four decades. Before the Great Recession, that number stood at 32 percent.

Pew pointed to declining employment, rising college enrollment, and fewer marriages for the rise in young adults living with their parents. Only 25 percent of Millennials were married in 2012, down from 30 percent of 18-31 year-olds in 2007.

Jed Kolko, chief economist for the real estate site Trulia, wrote earlier this month that “these young adults represent ‘pent-up demand’ for housing that the recovery should unleash. Problem is: the kids aren’t moving out yet.”

Kolko estimated that there were 2.4 million “missing households” in 2013 in large part because of young people living with their parents.