The Great Recession has been difficult on most Americans, but one demographic has been uniquely affected.

A Pew Research Center analysis of census data finds more than 21 million 18- to 31-year-olds are still living with their parents—that’s 36 percent of all Millennials.

For some perspective, in 1968, 56 percent of 18- to 31-year-olds were already married and independent. In 2012, just 23 percent of the same age demographic are married and living out on their own.