Millennials' most likely abode: Mom and Dad's

For the first time in modern history, more 18-to-34-year-olds live with their parents than in any other living arrangement, according to a Pew Research Center report released Tuesday.

In 2014, nearly one-third of young adults lived in their parents' home, a bigger group than those living with a spouse or romantic partner, living alone or with roommates, or living as single parents.

While millennials moving back with their parents have been the butt of jokes and hand-wringing for several years, and the recession of 2009 played a part in their doing so, this shift spans more than one generation. It has been decades in the making, a result of deep-rooted societal transformations in education, work and family building.

Since 1880, when the Census Bureau started keeping track, the most common arrangement for young people had been to live with a spouse or a significant other. That peaked in 1960, at 62 percent. But over the last 50 years, their options have opened up, making marriage just one of several possibilities.

As a result, the portion of young Americans settling down romantically has plunged to 31.6 percent, falling to second place for the first time.

"For earlier generations of young Americans, one of the major activities that they were focused on was partnering, forming a new family, maybe with children," said Richard Fry, the study's author. Now, they spend more time tending to studies and work, hoping to save enough to move out on their own.

A big reason is a decline in economic opportunities. As the cost of living has escalated and wages have stagnated, mounting student debt and rising home prices create obstacles to cohabitation and marriage.

"If you're not living with your parents, you're living with your roommates," said Laura Zelaya, 28, a news producer who lives with her parents in Falls Church, Virginia, while she saves to buy a house. Her brother and sister also came home after college. "I don't see a lot of people my age living alone."

The trend is led by young men, whose fortunes have been waning since the 1960s. While they have always lived with their parents in greater numbers than young women, this has been their dominant housing arrangement since 2009. In 2014, 35 percent lived with parents, while only 28 percent lived with a spouse or partner. For young women, the percentages are flipped: 29 with parents and 35 with partners; the difference is explained by the fact that young women tend to marry slightly older men.

Unemployed young men are more likely to live with their parents than young men with jobs, and employment among young men has dropped significantly in recent decades.

"I moved in with my parents because I don't really have to pay rent and I get free meals," said Marshall Taliaferro, 25, of Leesburg, Va.

Taliaferro, who works in his father's advertising agency and at a concert venue, says the setup is far from what he dreams of for himself.

"My ideal life is to be married, with maybe a kid or two, and at that point I would not be living with my parents; I would be living with my wife or girlfriend . . . and substantial enough pay. No parents would be lovely."

The trend has significant economic and demographic implications. People who delay starting families could face fertility challenges down the road, and in the near term, "the spending that goes on in the formation of a household - the furniture purchases, the appliance purchases, the cable subscriptions - that isn't happening," Fry said.

But the shift goes beyond economics. The marriage rate began to fall in the 1960s as options for young people were widening.

"The main driving force in the past for living apart from family was getting married, and people used to marry young," said Michael Rosenfeld, a sociology professor at Stanford University. "Part of the reason women lived with their parents was they couldn't afford to live on their own and there were social pressures against doing so."

But the introduction of the birth-control pill, the fading stigmas against premarital sex and out-of-wedlock childbirth, and the entry of more women into the workforce changed the landscape.

As a result, the median age of first marriage has risen from a 1956 low of 20 for women and 22 for men to 27 for women and 29 for men in 2014.

The trend is more pronounced among minorities, the study found, with 36 percent of black and Hispanic youths doing so.