The empty nests are filling up: For the first time in modern history, young adults ages 18 to 34 are more likely to live with a parent than with a romantic partner, according to a new census analysis by the Pew Research Center.

Millennials, who have been slower than previous generations to marry and set up their own households, reached that milestone in 2014, when 32.1 percent lived in a parent’s home, compared with 31.6 percent who lived with a spouse or a partner, the report found.

“The really seismic change is that we have so many fewer young adults partnering, either marrying or cohabiting,” said Richard Fry, the Pew economist who wrote the report. “In 1960, that silent generation left home earlier than any generation before or after, because they married so young.”

But in recent decades, fewer people have been marrying, and those who do are marrying at older ages. In 1960, the median age for a first marriage was 20 for women and 22 for men, and just one in 10 people over 25 had never married. Now, the median ages are 27 and 29, and one in five adults older than 25 has never married. In a 2014 study, Pew projected that a quarter of this generation of young adults might never marry.