Will society continue to treat twentysomethings as adults if they act more and more like teenagers?

Young adults marked a dubious milestone in 2014, according to the Pew Research Center: For the first time since at least 1940, more 18- to 34-year-old Americans were living with their parents than with a spouse or other romantic partner. Just under a third lived in each of these two arrangements, with the remainder living alone, with roommates, in dorms, etc. The trends have been especially stark since 1960, the apex of the young nuclear family in America. Living with romantic partners has plummeted, while living with parents has steadily grown.

This was hardly the first sign that something is up with young adults. It was more than half a decade ago—when I was a twentysomething myself and the economy had just taken its nosedive—when the New York Times published a much-discussed exploration of “emerging adulthood” by Robin Marantz Henig. Henig’s main expert source, the psychologist Jeffrey Jensen Arnett, argued that the twenties should be recognized as a new life phase distinct from full adulthood, similarly to what happened to adolescence at the beginning of the 20th century. But perhaps the most shocking assertion came from Henig’s 26-year-old daughter in a Slate symposium inspired by the piece: She said that almost none of her friends even considered themselves adults.

Back then, it was tempting to blame the immaturity of twentysomethings on the economy. That was a difficult case to make even during the recession, but with data through 2014 it’s impossible. It turns out that emerging adulthood is the result of numerous long-running demographic trends, and it is going to be a fact of life for the foreseeable future. That is to say, it won’t end when a new generation of young adults replaces us, the hated Millennials. 

Consider some of the trends at the heart of this new reality:

1. Americans are delaying both marriage and children.

This is the big one—in fact, Pew writes that “in some interpretations,” delayed marriage can explain “the entire increase in living with parents since 1960.” Holding off on marriage by definition decreases one’s likelihood of living with a spouse, and being unmarried and childless also lessens the pressure to move out of a parent’s home.

As Kay Hymowitz and her coauthors demonstrated in their report “Knot Yet,” the median age at first marriage and first childbirth have both been rising for decades—from the early 20s to the mid- to late 20s. There are important nuances here: For example, the trends “crossed over” in the late 1980s, so that the median age is now lower for first childbirth than for first marriage. Also, higher-class Americans wait to get married and then have kids, while poorer Americans have kids earlier and are more likely to be unmarried when they do.

In the aggregate, though, the pattern is simple. Americans are taking longer to achieve these traditional milestones of adulthood.

2. People are staying in school longer.

College graduates tend to get better jobs, and thus are more able to live separately from their parents, provided they’re not drowning in debt (see the next list item). But college is also a major reason so many are putting off marriage and kids to begin with, and young adults often live with their parents while they attend school. The percentage of the adult population with a college degree has grown more than sixfold since 1940.

3. Student-loan debt is growing.

One study found that “as student debt balances and prevalence trend ever upward, young consumers, on net, trend toward home.” The student-debt trend is indeed upward-sloping, and defaults doubled between 2000 and 2011, driven mainly by students at for-profit and non-selective schools.

4. Some young adults are opting out of the labor force.

Among those in their late teens and early 20s, it’s tempting to chalk this up to education. But young Americans have been participating in the work force less when they get beyond college age, too. In the early 1960s, only 2-3 percent of 25- to 34-year-old men were out of the labor force, meaning they were neither employed nor looking for a job; today, more than 10 percent are adrift. Women in this age range rushed into the labor force during the 1960s, ’70s, and ’80s, but then leveled off at roughly 75 percent participation. Needless to say, being out of the labor force can make things like marriage, children, and independent housing tricky.

Sure, some of these trends might change—we might finally get a handle on the student-loan mess or figure out a way to prod able-bodied young people into the workforce. But the more fundamental shifts aren’t going anywhere. Delayed childbearing, for example, is happening in part just because it can, thanks to birth control. And on education, most policymakers are actually clamoring to send more kids to college, not fewer, especially given the rising threat that automation poses to low-skill employment.

What does postponed adulthood mean for the law? Nothing, necessarily—but maybe a lot. Henig noted the legal relevance of maturity in 2010:

But what would it look like to extend some of the special status of adolescents to young people in their 20s? Our uncertainty about this question is reflected in our scattershot approach to markers of adulthood. People can vote at 18, but in some states they don’t age out of foster care until 21. They can join the military at 18, but they can’t drink until 21. They can drive at 16, but they can’t rent a car until 25 without some hefty surcharges. If they are full-time students, the Internal Revenue Service considers them dependents until 24; those without health insurance will soon be able to stay on their parents’ plans even if they’re not in school until age 26, or up to 30 in some states. …

If society decides to protect these young people or treat them differently from fully grown adults, how can we do this without becoming all the things that grown children resist—controlling, moralizing, paternalistic?

Maybe we can’t. Maybe as young Americans put off the responsibilities of adulthood, the rest of society will be less willing to treat them like adults.

Indeed, we might already be seeing the beginnings of this trend. Henig mentioned Obamacare’s provision allowing 26-year-olds to stay on their parents’ health insurance, but there are other examples where these age cutoffs have drifted upward, or where serious analysts have suggested raising them. Hawaii and California just hiked the smoking age to 21. Many states have imposed “graduated licensing,” where the driver’s license one earns at 16 no longer comes with full driving privileges; the minimum age for driving at night, for example, can be as high as 18. A recent Washington Post op-ed by a pediatrician and a law professor suggested a minimum age of 25 to own a gun.

Then, of course, there’s the rising tendency of colleges to infantilize their (legally adult) charges. Bluntly justifying campus restrictions on speech, one professor wrote that “students are children. Not in terms of age, but in terms of maturity. Even in college, they must be protected like children while being prepared to be adults.”

Such arguments only become more believable as, long after college, more young adults find themselves moving back home.

Robert VerBruggen is managing editor of The American Conservative. Twitter: @RAVerBruggen