These should be boom times for sex.

The share of Americans who say sex between unmarried adults is “not wrong at all” is at an all-time high. New cases of HIV are at an all-time low. Most women can—at last—get birth control for free, and the morning-after pill without a prescription.

If hookups are your thing, Grindr and Tinder offer the prospect of casual sex within the hour. The phrase If something exists, there is porn of it used to be a clever internet meme; now it’s a truism. BDSM plays at the local multiplex—but why bother going? Sex is portrayed, often graphically and sometimes gorgeously, on prime-time cable. Sexting is, statistically speaking, normal.

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Polyamory is a household word. Shame-laden terms like perversion have given way to cheerful-sounding ones like kink. Anal sex has gone from final taboo to “fifth base”—Teen Vogue (yes, Teen Vogue) even ran a guide to it. With the exception of perhaps incest and bestiality—and of course nonconsensual sex more generally—our culture has never been more tolerant of sex in just about every permutation.

But despite all this, American teenagers and young adults are having less sex.

To the relief of many parents, educators, and clergy members who care about the health and well-being of young people, teens are launching their sex lives later. From 1991 to 2017, the Centers for Disease Control and Prevention’s Youth Risk Behavior Survey finds, the percentage of high-school students who’d had intercourse dropped from 54 to 40 percent. In other words, in the space of a generation, sex has gone from something most high-school students have experienced to something most haven’t. (And no, they aren’t having oral sex instead—that rate hasn’t changed much.)

Meanwhile, the U.S. teen pregnancy rate has plummeted to a third of its modern high. When this decline started, in the 1990s, it was widely and rightly embraced. But now some observers are beginning to wonder whether an unambiguously good thing might have roots in less salubrious developments. Signs are gathering that the delay in teen sex may have been the first indication of a broader withdrawal from physical intimacy that extends well into adulthood.

Over the past few years, Jean M. Twenge, a psychology professor at San Diego State University, has published research exploring how and why Americans’ sex lives may be ebbing. In a series of journal articles and in her latest book, iGen, she notes that today’s young adults are on track to have fewer sex partners than members of the two preceding generations. People now in their early 20s are two and a half times as likely to be abstinent as Gen Xers were at that age; 15 percent report having had no sex since they reached adulthood.

Gen Xers and Baby Boomers may also be having less sex today than previous generations did at the same age. From the late 1990s to 2014, Twenge found, drawing on data from the General Social Survey, the average adult went from having sex 62 times a year to 54 times. A given person might not notice this decrease, but nationally, it adds up to a lot of missing sex. Twenge recently took a look at the latest General Social Survey data, from 2016, and told me that in the two years following her study, sexual frequency fell even further.

Some social scientists take issue with aspects of Twenge’s analysis; others say that her data source, although highly regarded, is not ideally suited to sex research. And yet none of the many experts I interviewed for this piece seriously challenged the idea that the average young adult circa 2018 is having less sex than his or her counterparts of decades past. Nor did anyone doubt that this reality is out of step with public perception—most of us still think that other people are having a lot more sex than they actually are.

When I called the anthropologist Helen Fisher, who studies love and sex and co-directs Match.com’s annual Singles in America survey of more than 5,000 unpartnered Americans, I could almost feel her nodding over the phone. “The data is that people are having less sex,” she said, with a hint of mischief. “I’m a Baby Boomer, and apparently in my day we were having a lot more sex than they are today!” She went on to explain that the survey has been probing the intimate details of people’s lives for eight years now. “Every year the whole Match company is rather staggered at how little sex Americans are having—including the Millennials.”

Fisher, like many other experts, attributes the sex decline to a decline in couplehood among young people. For a quarter century, fewer people have been marrying, and those who do have been marrying later. At first, many observers figured that the decline in marriage was explained by an increase in unmarried cohabitation—yet the share of people living together hasn’t risen enough to offset the decline in marriage: About 60 percent of adults under age 35 now live without a spouse or a partner. One in three adults in this age range live with their parents, making that the most common living arrangement for the cohort. People who live with a romantic partner tend to have sex more than those who don’t—and living with your parents is obviously bad for your sex life. But this doesn’t explain why young people are partnering up less to begin with.

Over the course of many conversations with sex researchers, psychologists, economists, sociologists, therapists, sex educators, and young adults, I heard many other theories about what I have come to think of as the sex recession. I was told it might be a consequence of the hookup culture, of crushing economic pressures, of surging anxiety rates, of psychological frailty, of widespread antidepressant use, of streaming television, of environmental estrogens leaked by plastics, of dropping testosterone levels, of digital porn, of the vibrator’s golden age, of dating apps, of option paralysis, of helicopter parents, of careerism, of smartphones, of the news cycle, of information overload generally, of sleep deprivation, of obesity. Name a modern blight, and someone, somewhere, is ready to blame it for messing with the modern libido.

Some experts I spoke with offered more hopeful explanations for the decline in sex. For example, rates of childhood sexual abuse have decreased in recent decades, and abuse can lead to both precocious and promiscuous sexual behavior. And some people today may feel less pressured into sex they don’t want to have, thanks to changing gender mores and growing awareness of diverse sexual orientations, including asexuality. Maybe more people are prioritizing school or work over love and sex, at least for a time, or maybe they’re simply being extra deliberate in choosing a life partner—and if so, good for them.

Many—or all—of these things may be true. In a famous 2007 study, people supplied researchers with 237 distinct reasons for having sex, ranging from mystical (“I wanted to feel closer to God”) to lame (“I wanted to change the topic of conversation”). The number of reasons not to have sex must be at least as high. Still, a handful of suspects came up again and again in my interviews and in the research I reviewed—and each has profound implications for our happiness.

1. Sex for One

The retreat from sex is not an exclusively American phenomenon. Most countries don’t track their citizens’ sex lives closely, but those that try (all of them wealthy) are reporting their own sex delays and declines. One of the most respected sex studies in the world, Britain’s National Survey of Sexual Attitudes and Lifestyles, reported in 2001 that people ages 16 to 44 were having sex more than six times a month on average. By 2012, the rate had dropped to fewer than five times. Over roughly the same period, Australians in relationships went from having sex about 1.8 times a week to 1.4 times. Finland’s “Finsex” study found declines in intercourse frequency, along with rising rates of masturbation.

In the Netherlands, the median age at which people first have intercourse rose from 17.1 in 2012 to 18.6 in 2017, and other types of physical contact also got pushed back, even kissing. This news was greeted not with universal relief, as in the United States, but with some concern. The Dutch pride themselves on having some of the world’s highest rates of adolescent and young-adult well-being. If people skip a crucial phase of development, one educator warned—a stage that includes not only flirting and kissing but dealing with heartbreak and disappointment—might they be unprepared for the challenges of adult life?

Meanwhile, Sweden, which hadn’t done a national sex study in 20 years, recently launched one, alarmed by polling suggesting that Swedes, too, were having less sex. The country, which has one of the highest birth rates in Europe, is apparently disinclined to risk its fecundity. “If the social conditions for a good sex life—for example through stress or other unhealthy factors—have deteriorated,” the Swedish health minister at the time wrote in an op-ed explaining the rationale for the study, it is “a political problem.”

This brings us to fertility-challenged Japan, which is in the midst of a demographic crisis and has become something of a case study in the dangers of sexlessness. In 2005, a third of Japanese single people ages 18 to 34 were virgins; by 2015, 43 percent of people in this age group were, and the share who said they did not intend to get married had risen too. (Not that marriage was any guarantee of sexual frequency: A related survey found that 47 percent of married people hadn’t had sex in at least a month.)

For nearly a decade, stories in the Western press have tied Japan’s sexual funk to a rising generation of soushoku danshi—literally, “grass-eating boys.” These “herbivore men,” as they are known in English, are said to be ambivalent about pursuing either women or conventional success. The new taxonomy of Japanese sexlessness also includes terms for groups such as hikikomori (“shut-ins”), parasaito shinguru (“parasite singles,” people who live with their parents beyond their 20s), and otaku (“obsessive fans,” especially of anime and manga)—all of whom are said to contribute to sekkusu shinai shokogun (“celibacy syndrome”).

Early on, most Western accounts of all this had a heavy subtext of “Isn’t Japan wacky?” This tone has slowly given way to a realization that the country’s experience might be less a curiosity than a cautionary tale. Dismal employment prospects played an initial role in driving many men to solitary pursuits—but the culture has since moved to accommodate and even encourage those pursuits. Roland Kelts, a Japanese American writer and longtime Tokyo resident, has described “a generation that found the imperfect or just unexpected demands of real-world relationships with women less enticing than the lure of the virtual libido.”

Let’s consider this lure for a moment. Japan is among the world’s top producers and consumers of porn, and the originator of whole new porn genres, such as bukkake (don’t ask). It is also a global leader in the design of high-end sex dolls. What may be more telling, though, is the extent to which Japan is inventing modes of genital stimulation that no longer bother to evoke old-fashioned sex, by which I mean sex involving more than one person. A recent article in The Economist, titled “Japan’s Sex Industry Is Becoming Less Sexual,” described onakura shops, where men pay to masturbate while female employees watch, and explained that because many younger people see the very idea of intercourse as mendokusai—tiresome—“services that make masturbation more enjoyable are booming.”

In their 2015 book, Modern Romance, the sociologist Eric Klinenberg and the comedian Aziz Ansari (who earlier this year became infamous for a hookup gone awry) describe Ansari’s visit to Japan seeking insights into the future of sex. He concluded that much of what he’d read about herbivore men missed the mark. Herbivores, he found, were “interested in sexual pleasure”—just not “through traditional routes.” Among Japan’s more popular recent innovations, he notes, is “a single-use silicone egg that men fill with lubricant and masturbate inside.” One night in Tokyo, Ansari picks one up at a convenience store, heads back to his hotel, and—sorry for the visual—gives it a go. He finds it cold and awkward, but understands its purpose. “It was a way,” he writes, “to avoid putting yourself out there and having an actual experience with another person.”

Justin Metz / Mendelsund / Munday

From 1992 to 2014, the share of American men who reported masturbating in a given week doubled, to 54 percent, and the share of women more than tripled, to 26 percent. Easy access to porn is part of the story, of course; in 2014, 43 percent of men said they’d watched porn in the past week. The vibrator figures in, too—a major study 10 years ago found that just over half of adult women had used one, and by all indications it has only grown in popularity. (Makes, models, and features have definitely proliferated. If you don’t know your Fun Factory Bi Stronic Fusion pulsator from your Power Toyfriend, you can find them on Amazon, which has these and some 10,000 other options.)

This shift is particularly striking when you consider that Western civilization has had a major hang-up about masturbation going back at least as far as Onan. As Robert T. Michael and his co-authors recount in Sex in America, J. H. Kellogg, the cereal maker, urged American parents of the late 19th century to take extreme measures to keep their children from indulging, including circumcision without anesthetic and application of carbolic acid to the clitoris. Thanks in part to his message, masturbation remained taboo well into the 20th century. By the 1990s, when Michael’s book came out, references to masturbation were still greeted with “nervous titters or with shock and disgust,” despite the fact that the behavior was commonplace.

Today, masturbation is even more common, and fears about its effects—now paired with concerns about digital porn’s ubiquity—are being raised anew by a strange assortment of people, including the psychologist Philip Zimbardo, the director of the famous Stanford Prison Experiment, who is enjoying an unlikely second act as an antiporn activist. In his book Man, Interrupted, Zimbardo warns that “procrasturbation”—his unfortunate portmanteau for procrastination via masturbation—may be leading young men to fail academically, socially, and sexually. Gary Wilson, an Oregon man who runs a website called Your Brain on Porn, makes a similar claim. In a popular tedx talk, which features animal copulation as well as many (human) brain scans, Wilson argues that masturbating to internet porn is addictive, causes structural changes in the brain, and is producing an epidemic of erectile dysfunction.

These messages are echoed and amplified by a Salt Lake City–based nonprofit called Fight the New Drug—the “drug” being porn—which has delivered hundreds of presentations to schools and other organizations around the country, including, this spring, the Kansas City Royals. The website NoFap, an offshoot of a popular Reddit message board founded by a now-retired Google contractor, provides community members (“fapstronauts”) a program to quit “fapping”—masturbating. Further outside the mainstream, the far-right Proud Boys group has a “no wanks” policy, which prohibits masturbating more than once a month. The group’s founder, Gavin McInnes, who also co-founded Vice Media, has said that pornography and masturbation are making Millennials “not even want to pursue relationships.”

The truth appears more complicated. There is scant evidence of an epidemic of erectile dysfunction among young men. And no researcher I spoke with had seen compelling evidence that porn is addictive. As the authors of a recent review of porn research note in The Archives of Sexual Behavior, “The notion of problematic pornography use remains contentious in both academic and popular literature,” while “the mental health community at large is divided as to the addictive versus non-addictive nature of Internet pornography.”

This isn’t to say there’s no correlation between porn use and desire for real-life sex. Ian Kerner, a well-known New York sex therapist and the author of several popular books about sex, told me that while he doesn’t see porn use as unhealthy (he recommends certain types of porn to some patients), he works with a lot of men who, inspired by porn, “are still masturbating like they’re 17,” to the detriment of their sex life. “It’s taking the edge off their desire,” he said. Kerner believes this is why more and more of the women coming to his office in recent years report that they want sex more than their partners do.

In reporting this story, I spoke and corresponded with dozens of 20- and early-30-somethings in hopes of better understanding the sex recession. I can’t know that they were representative, though I did seek out people with a range of experiences. I talked with some who had never had a romantic or sexual relationship, and others who were wildly in love or had busy sex lives or both. Sex may be declining, but most people are still having it—even during an economic recession, most people are employed.

The recession metaphor is imperfect, of course. Most people need jobs; that’s not the case with relationships and sex. I talked with plenty of people who were single and celibate by choice. Even so, I was amazed by how many 20-somethings were deeply unhappy with the sex-and-dating landscape; over and over, people asked me whether things had always been this hard. Despite the diversity of their stories, certain themes emerged.

One recurring theme, predictably enough, was porn. Less expected, perhaps, was the extent to which many people saw their porn life and their sex life as entirely separate things. The wall between the two was not absolute; for one thing, many straight women told me that learning about sex from porn seemed to have given some men dismaying sexual habits. (We’ll get to that later.) But by and large, the two things—partnered sex and solitary porn viewing—existed on separate planes. “My porn taste and partner taste are quite different,” one man in his early 30s told me, explaining that he watches porn about once a week and doesn’t think it has much effect on his sex life. “I watch it knowing it is fiction,” a 22-year-old woman said, adding that she didn’t “internalize” it.

I thought of these comments when Pornhub, the top pornography website, released its list of 2017’s most popular searches. In first place, for the third year running, was lesbian (a category beloved by men and women alike). The new runner-up, however, was hentai—anime, manga, and other animated porn. Porn has never been like real sex, of course, but hentai is not even of this world; unreality is the source of its appeal. In a New York–magazine cover story on porn preferences, Maureen O’Connor described the ways hentai transmogrifies body parts (“eyes bigger than feet, breasts the size of heads, penises thicker than waists”) and eroticizes the supernatural (“sexy human shapes” combine with “candy-colored fur and animal horns, ears, and tails”). In other words, the leading search category for porn involves sex that half the population doesn’t have the equipment to engage in, and the runner-up isn’t carnal so much as hallucinatory.

Many of the younger people I talked with see porn as just one more digital activity—a way of relieving stress, a diversion. It is related to their sex life (or lack thereof) in much the same way social media and binge-watching TV are. As one 24-year-old man emailed me:

The internet has made it so easy to gratify basic social and sexual needs that there’s far less incentive to go out into the “meatworld” and chase those things. This isn’t to say that the internet can give you more satisfaction than sex or relationships, because it doesn’t … [But it can] supply you with just enough satisfaction to placate those imperatives … I think it’s healthy to ask yourself: “If I didn’t have any of this, would I be going out more? Would I be having sex more?” For a lot of people my age, I think the answer is probably yes.

Even people in relationships told me that their digital life seemed to be vying with their sex life. “We’d probably have a lot more sex,” one woman noted, “if we didn’t get home and turn on the TV and start scrolling through our phones.” This seems to defy logic; our hunger for sex is supposed to be primal. Who would pick messing around online over actual messing around?

Teenagers, for one. An intriguing study published last year in the Journal of Population Economics examined the introduction of broadband internet access at the county-by-county level, and found that its arrival explained 7 to 13 percent of the teen-birth-rate decline from 1999 to 2007.

Maybe adolescents are not the hormone-crazed maniacs we sometimes make them out to be. Maybe the human sex drive is more fragile than we thought, and more easily stalled.

2. Hookup Culture and Helicopter Parents

I started high school in 1992, around the time the teen pregnancy and birth rates hit their highest levels in decades, and the median age at which teenagers began having sex was approaching its modern low of 16.9. Women born in 1978, the year I was born, have a dubious honor: We were younger when we started having sex than any group since.

But as the ’90s continued, the teen pregnancy rate began to decline. This development was welcomed—even if experts couldn’t agree on why it was happening. Birth-control advocates naturally pointed to birth control. And yes, teenagers were getting better about using contraceptives, but not sufficiently better to single-handedly explain the change. Christian pro-abstinence groups and backers of abstinence-only education, which received a big funding boost from the 1996 welfare-reform act, also tried to take credit. Yet the teen pregnancy rate was falling even in places that hadn’t adopted abstinence-only curricula, and research has since shown that virginity pledges and abstinence-only education don’t actually beget abstinence.

Still, the trend continued: Each wave of teenagers had sex a little later, and the pregnancy rate kept inching down. You wouldn’t have known either of these things, though, from all the hyperventilating about hookup culture that started in the late ’90s. The New York Times, for example, announced in 1997 that on college campuses, casual sex “seems to be near an all-time high.” It didn’t offer much data to support this, but it did introduce the paper’s readers to the term hooking up, which it defined as “anything from 20 minutes of strenuous kissing to spending the night together fully clothed to sexual intercourse.”

Pretty much ever since, people have been overestimating how much casual sex high-school and college students are having (even, surveys show, students themselves). In the past several years, however, a number of studies and books on hookup culture have begun to correct the record. One of the most thoughtful of these is American Hookup: The New Culture of Sex on Campus, by Lisa Wade, a sociology professor at Occidental College. The book draws on detailed journals kept by students at two liberal-arts colleges from 2010 to 2015, as well as on Wade’s conversations with students at 24 other colleges and universities.

Wade sorts the students she followed into three groups. Roughly one-third were what she calls “abstainers”—they opted out of hookup culture entirely. A little more than a third were “dabblers”—they hooked up sometimes, but ambivalently. Less than a quarter were “enthusiasts,” who delighted in hooking up. The remainder were in long-term relationships.

This portrait is compatible with a 2014 study finding that Millennial college students weren’t having more sex or sexual partners than their Gen X predecessors. It also tracks with data from the Online College Social Life Survey, a survey of more than 20,000 college students that was conducted from 2005 to 2011, which found the median number of hookups over a four-year college career to be five—a third of which involved only kissing and touching. The majority of students surveyed said they wished they had more opportunities to find a long-term boyfriend or girlfriend.

When I spoke with Wade recently, she told me that she found the sex decline among teens and 20-somethings completely unsurprising—young people, she said, have always been most likely to have sex in the context of a relationship. “Go back to the point in history where premarital sex became more of a thing, and the conditions that led to it,” she said, referring to how post–World War II anxiety about a man shortage led teen girls in the late 1940s and ’50s to pursue more serious romantic relationships than had been customary before the war. “Young women, at that point, innovate ‘going steady,’ ” Wade said, adding that parents were not entirely happy about the shift away from prewar courtship, which had favored casual, nonexclusive dating. “If you [go out with someone for] one night you might get up to a little bit of necking and petting, but what happens when you spend months with them? It turns out 1957 has the highest rate of teen births in American history.”

“We hook up because we have no social skills. We have no social skills because we hook up.”

In more recent decades, by contrast, teen romantic relationships appear to have grown less common. In 1995, the large longitudinal study known as “Add Health” found that 66 percent of 17-year-old men and 74 percent of 17-year-old women had experienced “a special romantic relationship” in the past 18 months. In 2014, when the Pew Research Center asked 17-year-olds whether they had “ever dated, hooked up with or otherwise had a romantic relationship with another person”—seemingly a broader category than the earlier one—only 46 percent said yes.

So what thwarted teen romance? Adolescence has changed so much in the past 25 years that it’s hard to know where to start. As Jean Twenge wrote in The Atlantic last year, the percentage of teens who report going on dates has decreased alongside the percentage who report other activities associated with entering adulthood, like drinking alcohol, working for pay, going out without one’s parents, and getting a driver’s license.

These shifts coincide with another major change: parents’ increased anxiety about their children’s educational and economic prospects. Among the affluent and educated, especially, this anxiety has led to big changes in what’s expected of teens. “It’s hard to work in sex when the baseball team practices at 6:30, school starts at 8:15, drama club meets at 4:15, the soup kitchen starts serving at 6, and, oh yeah, your screenplay needs completion,” said a man who was a couple of years out of college, thinking back on his high-school years. He added: “There’s immense pressure” from parents and other authority figures “to focus on the self, at the expense of relationships”—pressure, quite a few 20-somethings told me, that extends right on through college.

Malcolm Harris strikes a similar note in his book, Kids These Days: Human Capital and the Making of Millennials. Addressing the desexing of the American teenager, he writes:

A decline in unsupervised free time probably contributes a lot. At a basic level, sex at its best is unstructured play with friends, a category of experience that … time diaries … tell us has been decreasing for American adolescents. It takes idle hands to get past first base, and today’s kids have a lot to do.

Marriage 101, one of the most popular undergraduate classes at Northwestern University, was launched in 2001 by William M. Pinsof, a founding father of couples therapy, and Arthur Nielsen, a psychiatry professor. What if you could teach about love, sex, and marriage before people chose a partner, Pinsof and Nielsen wondered—before they developed bad habits? The class was meant to be a sort of preemptive strike against unhappy marriages. Under Alexandra Solomon, the psychology professor who took over the course six years ago, it has become, secondarily, a strike against what she sees as the romantic and sexual stunting of a generation. She assigns students to ask someone else out on a date, for example, something many have never done.

This hasn’t hurt the class’s appeal; during registration, it fills within minutes. (It may or may not have helped that a course with overlapping appeal, Human Sexuality, was discontinued some years back after its professor presided over a demonstration of something called a fucksaw.) Each week during office hours, students wait in line to talk with Solomon, who is also a practicing therapist at the university’s Family Institute, not only about the class but about their love woes and everything they don’t know about healthy and pleasurable sex—which, in many cases, is a lot.

Over the course of numerous conversations, Solomon has come to various conclusions about hookup culture, or what might more accurately be described as lack-of-relationship culture. For one thing, she believes it is both a cause and an effect of social stunting. Or, as one of her students put it to her: “We hook up because we have no social skills. We have no social skills because we hook up.” For another, insofar as her students find themselves choosing between casual sex and no sex, they are doing so because an obvious third option—relationship sex—strikes many of them as not only unattainable but potentially irresponsible. Most Marriage 101 students have had at least one romantic relationship over the course of their college career; the class naturally attracts relationship-oriented students, she points out. Nonetheless, she believes that many students have absorbed the idea that love is secondary to academic and professional success—or, at any rate, is best delayed until those other things have been secured. “Over and over,” she has written, “my undergraduates tell me they try hard not to fall in love during college, imagining that would mess up their plans.”

One Friday afternoon in March, I sat in on a discussion Solomon was hosting for a group of predominantly female graduate students in the Family Institute’s counseling programs, on the challenges of love and sex circa 2018. Over rosé and brownies, students shared thoughts on topics ranging from Aziz Ansari’s notorious date (which had recently been detailed on the website Babe) to the ambiguities of current relationship terminology. “People will be like, ‘We’re dating, we’re exclusive, but we’re not boyfriend and girlfriend.’ What does that mean?” one young woman asked, exasperated. A classmate nodded emphatically. “What does that mean? We’re in a monogamous relationship, but …” She trailed off. Solomon jumped in with a sort of relationship litmus test: “If I get the flu, are you bringing me soup?” Around the conference table, heads shook; not many people were getting (or giving) soup.

The conversation proceeded to why soup-bringing relationships weren’t more common. “You’re supposed to have so much before you can get into a relationship,” one woman offered. Another said that when she was in high school, her parents, who are both professionals with advanced degrees, had discouraged relationships on the grounds that they might diminish her focus. Even today, in graduate school, she was finding the attitude hard to shake. “Now I need to finish school, I need to get a practice going, I need to do this and this, and then I’ll think about love. But by 30, you’re like, What is love? What’s it like to be in love?”

He couldn’t escape the sense that hitting on someone in person had, in a short period of time, gone from normal behavior to borderline creepy.

In early May, I returned to Northwestern to sit in on a Marriage 101 discussion section. I had picked that particular week because the designated topic, “Sex in Intimate Relationships,” seemed relevant. As it happened, though, there wasn’t much talk of sex; the session was mostly consumed by a rapturous conversation about the students’ experiences with something called the “mentor couple” assignment, which had involved interviewing a couple in the community and chronicling their relationship.

“To see a relationship where two people are utterly content and committed,” one woman said, with real conviction, “it’s kind of an aha moment for me.” Another student spoke disbelievingly of her couple’s pre-smartphone courtship. “I couldn’t necessarily relate to it,” she said. “They met, they got each other’s email addresses, they emailed one another, they went on a first date, they knew that they were going to be together. They never had a ‘define the relationship’ moment, because both were on the same page. I was just like, Damn, is that what it’s supposed to be like?” About two-thirds of the way through the allotted discussion time, one of the teaching assistants finally interrupted. “Should we transition?” she asked, tentatively. “I wanted to transition to talk about sex. Which is the topic of this week.”

3. The Tinder Mirage

Simon, a 32-year-old grad student who describes himself as short and balding (“If I wasn’t funny,” he says, “I’d be doomed”), didn’t lack for sex in college. (The names of people who talked with me about their personal lives have been changed.) “I’m outgoing and like to talk, but I am at heart a significant nerd,” he told me when we spoke recently. “I was so happy that college had nerdy women. That was a delight.” Shortly before graduation, he started a relationship that lasted for seven years. When he and his girlfriend broke up, in 2014, he felt like he’d stepped out of a time machine.

Before the relationship, Tinder didn’t exist; nor did iPhones. Simon wasn’t particularly eager to get into another serious relationship right away, but he wanted to have sex. “My first instinct was go to bars,” he said. But each time he went to one, he struck out. He couldn’t escape the sense that hitting on someone in person had, in a short period of time, gone from normal behavior to borderline creepy. His friends set up a Tinder account for him; later, he signed up for Bumble, Match, OkCupid, and Coffee Meets Bagel.

Unless you are exceptionally good-looking, the thing online dating may be best at is sucking up large amounts of time.

He had better luck with Tinder than the other apps, but it was hardly efficient. He figures he swiped right—indicating that he was interested—up to 30 times for every woman who also swiped right on him, thereby triggering a match. But matching was only the beginning; then it was time to start messaging. “I was up to over 10 messages sent for a single message received,” he said. In other words: Nine out of 10 women who matched with Simon after swiping right on him didn’t go on to exchange messages with him. This means that for every 300 women he swiped right on, he had a conversation with just one.

At least among people who don’t use dating apps, the perception exists that they facilitate casual sex with unprecedented efficiency. In reality, unless you are exceptionally good-looking, the thing online dating may be best at is sucking up large amounts of time. As of 2014, when Tinder last released such data, the average user logged in 11 times a day. Men spent 7.2 minutes per session and women spent 8.5 minutes, for a total of about an hour and a half a day. Yet they didn’t get much in return. Today, the company says it logs 1.6 billion swipes a day, and just 26 million matches. And, if Simon’s experience is any indication, the overwhelming majority of matches don’t lead to so much as a two-way text exchange, much less a date, much less sex.

When I talked with Simon, he was seven months into a relationship with a new girlfriend, whom he’d met through another online-dating service. He liked her, and was happy to be on hiatus from Tinder. “It’s like howling into the void for most guys,” he explained, “and like searching for a diamond in a sea of dick pics for most girls.”

So why do people continue to use dating apps? Why not boycott them all? Simon said meeting someone offline seemed like less and less of an option. His parents had met in a chorus a few years after college, but he couldn’t see himself pulling off something similar. “I play volleyball,” he added. “I had somebody on the volleyball team two years ago who I thought was cute, and we’d been playing together for a while.” Simon wanted to ask her out, but ultimately concluded that this would be “incredibly awkward,” even “boorish.”

At first, I wondered whether Simon was being overly genteel, or a little paranoid. But the more people I talked with, the more I came to believe that he was simply describing an emerging cultural reality. “No one approaches anyone in public anymore,” said a teacher in Northern Virginia. “The dating landscape has changed. People are less likely to ask you out in real life now, or even talk to begin with,” said a 28-year-old woman in Los Angeles who volunteered that she had been single for three years.

As romance and its beginnings are segregated from the routines of daily life, there is less and less space for elevator flirtation.

This shift seems to be accelerating amid the national reckoning with sexual assault and harassment, and a concomitant shifting of boundaries. According to a November 2017 Economist/YouGov poll, 17 percent of Americans ages 18 to 29 now believe that a man inviting a woman out for a drink “always” or “usually” constitutes sexual harassment. (Among older groups, much smaller percentages believe this.)

Laurie Mintz, who teaches a popular undergraduate class on the psychology of sexuality at the University of Florida, told me that the #MeToo movement has made her students much more aware of issues surrounding consent. She has heard from many young men who are productively reexamining their past actions and working diligently to learn from the experiences of friends and partners. But others have described less healthy reactions, like avoiding romantic overtures for fear that they might be unwelcome. In my own conversations, men and women alike spoke of a new tentativeness and hesitancy. One woman who described herself as a passionate feminist said she felt empathy for the pressure that heterosexual dating puts on men. “I think I owe it to them, in this current cultural moment particularly, to try to treat them like they’re human beings taking a risk talking to a stranger,” she wrote me. “There are a lot of lonely, confused people out there, who have no idea what to do or how to date.”

I mentioned to several of the people I interviewed for this piece that I’d met my husband in an elevator, in 2001. (We worked on different floors of the same institution, and over the months that followed struck up many more conversations—in the elevator, in the break room, on the walk to the subway.) I was fascinated by the extent to which this prompted other women to sigh and say that they’d just love to meet someone that way. And yet quite a few of them suggested that if a random guy started talking to them in an elevator, they would be weirded out. “Creeper! Get away from me,” one woman imagined thinking. “Anytime we’re in silence, we look at our phones,” explained her friend, nodding. Another woman fantasized to me about what it would be like to have a man hit on her in a bookstore. (She’d be holding a copy of her favorite book. “What’s that book?” he’d say.) But then she seemed to snap out of her reverie, and changed the subject to Sex and the City reruns and how hopelessly dated they seem. “Miranda meets Steve at a bar,” she said, in a tone suggesting that the scenario might as well be out of a Jane Austen novel, for all the relevance it had to her life.

Video: The Sex Drought

How could various dating apps be so inefficient at their ostensible purpose—hooking people up—and still be so popular? For one thing, lots of people appear to be using them as a diversion, with limited expectations of meeting up in person. As Iris, who’s 33, told me bitterly, “They’ve gamified interaction. The majority of men on Tinder just swipe right on everybody. They say yes, yes, yes to every woman.”

Stories from other app users bear out the idea of apps as diversions rather than matchmakers. “Getting right-swiped is a good ego boost even if I have no intention of meeting someone,” one man told me. A 28-year-old woman said that she persisted in using dating apps even though she had been abstinent for three years, a fact she attributed to depression and low libido: “I don’t have much inclination to date someone.”

“After a while it just feels exactly the same as getting good at a bubble-popping game. I’m happy to be good at it, but what am I really achieving?” said an app user who described herself as abstinent by choice. Another woman wrote that she was “too lazy” to meet people, adding: “I usually download dating apps on a Tuesday when I’m bored, watching TV … I don’t try very hard.” Yet another woman said that she used an app, but only “after two glasses of white wine—then I promptly delete it after two hours of fruitless swiping.”

Many critiques of online dating, including a 2013 article by Dan Slater in The Atlantic, adapted from his book A Million First Dates, have focused on the idea that too many options can lead to “choice overload,” which in turn leads to dissatisfaction. Online daters, he argued, might be tempted to keep going back for experiences with new people; commitment and marriage might suffer. Michael Rosenfeld, a sociologist who runs a longitudinal study out of Stanford called “How Couples Meet and Stay Together,” questions this hypothesis; his research finds that couples who meet online tend to marry more quickly than other couples, a fact that hardly suggests indecision.

Maybe choice overload applies a little differently than Slater imagined. Maybe the problem is not the people who date and date some more—they might even get married, if Rosenfeld is right—but those who are so daunted that they don’t make it off the couch. This idea came up many times in my conversations with people who described sex and dating lives that had gone into a deep freeze. Some used the term paradox of choice; others referred to option paralysis (a term popularized by Black Mirror); still others invoked fobo (“fear of a better option”).

And yet online dating continues to attract users, in part because many people consider apps less stressful than the alternatives. Lisa Wade suspects that graduates of high-school or college hookup culture may welcome the fact that online dating takes some of the ambiguity out of pairing up (We’ve each opted in; I’m at least a little bit interested in you). The first time my husband and I met up outside work, neither of us was sure whether it was a date. When you find someone via an app, there’s less uncertainty.

As a 27-year-old woman in Philadelphia put it: “I have insecurities that make fun bar flirtation very stressful. I don’t like the Is he into me? moment. I use dating apps because I want it to be clear that this is a date and we are sexually interested in one another. If it doesn’t work out, fine, but there’s never a Is he asking me to hang as a friend or as a date? feeling.” Other people said they liked the fact that on an app, their first exchanges with a prospective date could play out via text rather than in a face-to-face or phone conversation, which had more potential to be awkward.

Anna, who graduated from college three years ago, told me that in school, she struggled to “read” people. Dating apps have been a helpful crutch. “There’s just no ambiguity,” she explained. “This person is interested in me to some extent.” The problem is that the more Anna uses apps, the less she can imagine getting along without them. “I never really learned how to meet people in real life,” she said. She then proceeded to tell me about a guy she knew slightly from college, whom she’d recently bumped into a few times. She found him attractive and wanted to register her interest, but wasn’t sure how to do that outside the context of a college party. Then she remembered that she’d seen his profile on Tinder. “Maybe next time I sign in,” she said, musing aloud, “I’ll just swipe right so I don’t have to do this awkward thing and get rejected.”

Apart from helping people avoid the potential embarrassments (if also, maybe, the exhilaration) of old-fashioned flirting, apps are quite useful to those who are in what economists call “thin markets”—markets with a relatively low number of participants. Sexual minorities, for example, tend to use online dating services at much higher rates than do straight people. (Michael Rosenfeld—whose survey deliberately oversampled gays and lesbians in an effort to compensate for the dearth of research on their dating experiences—finds that “unpartnered gay men and unpartnered lesbians seem to have substantially more active dating lives than do heterosexuals,” a fact he attributes partly to their successful use of apps. This disparity raises the possibility that the sex recession may be a mostly heterosexual phenomenon.)

Justin Metz / Pablo Delcan

In all dating markets, apps appear to be most helpful to the highly photogenic. As Emma, a 26-year-old virgin who sporadically tries her luck with online dating, glumly told me, “Dating apps make it easy for hot people—who already have the easiest time.” Christian Rudder, a co-founder of OkCupid (one of the less appearance-centric dating services, in that it encourages detailed written profiles), reported in 2009 that the male users who were rated most physically attractive by female users got 11 times as many messages as the lowest-rated men did; medium-rated men received about four times as many messages. The disparity was starker for women: About two-thirds of messages went to the one-third of women who were rated most physically attractive. A more recent study by researchers at the University of Michigan and the Santa Fe Institute found that online daters of both genders tend to pursue prospective mates who are on average 25 percent more desirable than they are—presumably not a winning strategy.

The very existence of online dating makes it harder for anyone to make an overture in person without seeming inappropriate.

So where does this leave us? Many online daters spend large amounts of time pursuing people who are out of their league. Few of their messages are returned, and even fewer lead to in-person contact. At best, the experience is apt to be bewildering (Why are all these people swiping right on me, then failing to follow through?). But it can also be undermining, even painful. Emma is, by her own description, fat. She is not ashamed of her appearance, and purposefully includes several full-body photos in her dating profiles. Nevertheless, men persist in swiping right on her profile only to taunt her—when I spoke with her, one guy had recently ended a text exchange by sending her a gif of an overweight woman on a treadmill.

An even bigger problem may be the extent to which romantic pursuit is now being cordoned off into a predictable, prearranged online venue, the very existence of which makes it harder for anyone, even those not using the apps, to extend an overture in person without seeming inappropriate. What a miserable impasse.

4. Bad Sex (Painfully Bad)

One especially springlike morning in May, as Debby Herbenick and I walked her baby through a park in Bloomington, Indiana, she shared a bit of advice she sometimes offers students at Indiana University, where she is a leading sex researcher. “If you’re with somebody for the first time,” she said evenly, “don’t choke them, don’t ejaculate on their face, don’t try to have anal sex with them. These are all things that are just unlikely to go over well.”

I’d sought out Herbenick in part because I was intrigued by an article she’d written for The Washington Post proposing that the sex decline might have a silver lining. Herbenick had asked whether we might be seeing, among other things, a retreat from coercive or otherwise unwanted sex. Just a few decades ago, after all, marital rape was still legal in many states. As she pushed her daughter’s stroller, she elaborated on the idea that some of the sex recession’s causes could be a healthy reaction to bad sex—a subset of people “not having sex that they don’t want to have anymore. People feeling more empowered to say ‘No thanks.’ ”

Bloomington is the unofficial capital of American sex research, a status that dates back to the 1940s, when the Indiana University biologist Alfred Kinsey’s pioneering sex surveys inaugurated the field. It retains its standing thanks partly to the productivity of its scientists, and partly to the paucity of sex research at other institutions. In 2009, Herbenick and her colleagues launched the ongoing National Survey of Sexual Health and Behavior, which is only the second nationally representative survey to examine Americans’ sex lives in detail—and the first to try to chart them over time. (The previous national survey, out of the University of Chicago, was conducted just once, in 1992. Most other sex research, including Kinsey’s, has used what are known as convenience samples, which don’t represent the population at large. The long-running General Social Survey, which much of Jean Twenge’s research is based upon, is nationally representative, but poses only a few questions about sex.)

I asked Herbenick whether the NSSHB’s findings gave her any hunches about what might have changed since the 1990s. She mentioned the new popularity of sex toys, and a surge in heterosexual anal sex. Back in 1992, the big University of Chicago survey reported that 20 percent of women in their late 20s had tried anal sex; in 2012, the NSSHB found a rate twice that. She also told me about new data suggesting that, compared with previous generations, young people today are more likely to engage in sexual behaviors prevalent in porn, like the ones she warns her students against springing on a partner. All of this might be scaring some people off, she thought, and contributing to the sex decline.

“If you are a young woman,” she added, glancing down at her daughter, “and you’re having sex and somebody tries to choke you, I just don’t know if you’d want to go back for more right away.”

Justin Metz / Pablo Delcan

Some of Herbenick’s most sobering research concerns the prevalence of painful sex. In 2012, 30 percent of women said they’d experienced pain the last time they’d had vaginal intercourse; during anal intercourse, 72 percent had. Whether or not these rates represent an increase (we have no basis for comparison), they are troublingly high. Moreover, most women don’t tell their partners about their pain. J. Dennis Fortenberry, the chief of adolescent medicine at Indiana University’s medical school and a co-leader of the NSSHB, believes that many girls and women have internalized the idea that physical discomfort goes with being female.

A particularly vivid illustration of this comes from Lucia O’Sullivan, a University of New Brunswick psychology professor who has published research documenting high rates of sexual dysfunction among adolescents and young adults. That work grew out of a lunch several years ago with a physician from the university’s student-health center, who told O’Sullivan that she was deeply concerned by all the vulvar fissures she and her colleagues were seeing in their student patients. These women weren’t reporting rape, but the condition of their genitals showed that they were enduring intercourse that was, literally, undesired. “They were having sex they didn’t want, weren’t aroused by,” O’Sullivan says. The physician told her that the standard of care was to hand the women K‑Y Jelly and send them on their way.

Painful sex is not new, but there’s reason to think that porn may be contributing to some particularly unpleasant early sexual experiences. Studies show that, in the absence of high-quality sex education, teen boys look to porn for help understanding sex—anal sex and other acts women can find painful are ubiquitous in mainstream porn. (This isn’t to say that anal sex has to be painful, but rather that the version most women are experiencing is.) In a series of in-depth interviews, Cicely Marston of the London School of Hygiene and Tropical Medicine found that teenage boys experimenting with anal sex—perhaps influenced by what they’ve seen in porn—may find that sudden, unlubricated penetration is more difficult than it looks, and more agonizing for the recipient. Some of her subjects appear to have pressured their partner; others seem to have resorted to what another researcher described to me, clinically, as “nonconsensual substitution of anal for vaginal sex.”

In my interviews with young women, I heard too many iterations to count of “he did something I didn’t like that I later learned is a staple in porn,” choking being one widely cited example. Outside of porn, some people do enjoy what’s known as erotic asphyxiation—they say restricting oxygen to the brain can make for more intense orgasms—but it is dangerous and ranks high on the list of things you shouldn’t do to someone unless asked to. Tess, a 31-year-old woman in San Francisco, mentioned that her past few sexual experiences had been with slightly younger men. “I’ve noticed that they tend to go for choking without prior discussion,” she said. Anna, the woman who described how dating apps could avert awkwardness, told me she’d been choked so many times that at first, she figured it was normal. “A lot of people don’t realize you have to ask,” she said.

As Marina Adshade, a professor at the University of British Columbia who studies the economics of sex and love, said to me, “Men have bad sex and good sex. But when sex is bad for women, it’s really, really bad. If women are avoiding sex, are they trying to avoid the really bad sex?”

Sex takes time to learn under the best of circumstances, and these are not the best of circumstances. Modeling your behavior after what you’ve seen on-screen can lead to what’s known as “spectatoring”—that is, worrying about how you look and sound while you’re having sex, a behavior the sex researchers William H. Masters and Virginia E. Johnson long ago posited was bad for sexual functioning. Some young women told me they felt pressured to emulate porn actresses—and to achieve orgasm from penetration alone, which most women can’t do. “It took me a while to be comfortable with the fact that I don’t have to be as vocal during sex as the girls seem to be in porn,” a 24-year-old woman in Boston said. A 31-year-old in Phoenix explained that in her experience, porn has made men “expect that they can make any woman orgasm by just pounding away.”

Learning sex in the context of one-off hookups isn’t helping either. Research suggests that, for most people, casual sex tends to be less physically pleasurable than sex with a regular partner. Paula England, a sociologist at NYU who has studied hookup culture extensively, attributes this partly to the importance of “partner-specific sexual skills”—that is, knowing what your partner likes. For women, especially, this varies greatly. One study found that while hooking up with a new partner, only 31 percent of men and 11 percent of women reached orgasm. (By contrast, when people were asked about their most recent sexual encounter in the context of a relationship, 84 percent of men and 67 percent of women said they’d had an orgasm.) Other studies have returned similar results. Of course, many people enjoy encounters that don’t involve orgasms—a third of hookups don’t include acts that could reasonably be expected to lead to one—but the difference between the two contexts is striking. If young people are delaying serious relationships until later in adulthood, more and more of them may be left without any knowledge of what good sex really feels like.

As I was reporting this piece, quite a few people told me that they were taking a break from sex and dating. This tracks with research by Lucia O’Sullivan, who finds that even after young adults’ sex lives start up, they are often paused for long periods of time. Some people told me of sexual and romantic dormancy triggered by assault or depression; others talked about the decision to abstain as if they were taking a sabbatical from an unfulfilling job.

Late one afternoon in February, I met up with Iris, the woman who remarked to me that Tinder had been “gamified,” at the Lemon Collective, a design studio and workshop space in the Petworth neighborhood of Washington, D.C. The collective hosts DIY and design classes as well as courses geared toward the wellness of Millennial women; Valentine’s Day had been celebrated with a wildly oversubscribed real-estate workshop called “House Before Spouse.” (“We don’t need partners to be financially savvy and create personal wealth,” the event’s description said. “Wine and cheese will be served, obviously.”)

As we chatted (over, obviously, wine), Iris despaired at the quality of her recent sexual interactions. “I had such bad sex yesterday, my God, it was so bad,” she said wearily. “He basically got it in and—” She banged a fist against her palm at a furious tempo. It was the first time she’d slept with this man, whom she had met on Tinder, and she wondered aloud whether she could coach him. She was doubtful, though; he was in his 30s—old enough, she thought, to know better.

Iris observed that her female friends, who were mostly single, were finding more and more value in their friendships. “I’m 33, I’ve been dating forever, and, you know, women are better,” she said. “They’re just better.” She hastened to add that men weren’t bad; in fact, she hated how anti-male the conversations around her had grown. Still, she and various platonic female friends—most of whom identified as straight—were starting to play roles in one another’s lives that they might not be playing if they had fulfilling romantic or sexual relationships. For instance, they’d started trading lesbian-porn recommendations, and were getting to know one another’s preferences pretty well. Several women also had a text chain going in which they exchanged nude photos of themselves. “It’s nothing but positivity,” she said, describing the complimentary texts they’d send one another in reply to a photo (“Damn, girl, your tits!”). She wasn’t ready to swear off men entirely. But, she said, “I want good sex.” Or at least, she added, “pretty good sex.”

5. Inhibition

“Millennials don’t like to get naked—if you go to the gym now, everyone under 30 will put their underwear on under the towel, which is a massive cultural shift,” Jonah Disend, the founder of the branding consultancy Redscout, told Bloomberg last year. He said that designs for master-bedroom suites were evolving for much the same reason: “They want their own changing rooms and bathrooms, even in a couple.” The article concluded that however “digitally nonchalant” Millennials might seem—an allusion, maybe, to sexting—“they’re prudish in person.” Fitness facilities across the country are said to be renovating locker rooms in response to the demands of younger clients. “Old-timers, guys that are 60-plus, have no problem with a gang shower,” one gym designer told The New York Times, adding that Millennials require privacy.

Some observers have suggested that a new discomfort with nudity might stem from the fact that, by the mid-1990s, most high schools had stopped requiring students to shower after gym class. Which makes sense—the less time you spend naked, the less comfortable you are being naked. But people may also be newly worried about what they look like naked. A large and growing body of research reports that for both men and women, social-media use is correlated with body dissatisfaction. And a major Dutch study found that among men, frequency of pornography viewing was associated with concern about penis size. I heard much the same from quite a few men (“too hairy, not fit enough, not big enough in terms of penis size,” went one morose litany). According to research by Debby Herbenick, how people feel about their genitals predicts sexual functioning—and somewhere between 20 and 25 percent of people, perhaps influenced by porn or plastic-surgery marketing, feel negatively. The business of labiaplasty has become so lucrative, she told me in an email, “that you will actually see billboards (yes, billboards!) in some cities advertising it.”

As one might imagine, feeling comfortable in your body is good for your sex life. A review of 57 studies examining the relationship between women’s body image and sexual behavior suggests that positive body image is linked to having better sex. Conversely, not feeling comfortable in your own skin complicates sex. If you don’t want your partner to see you getting out of the shower, how is oral sex going to work?

Maybe, for some people, it isn’t. The 2017 iteration of Match.com’s Singles in America survey (co-led by Helen Fisher and the Kinsey Institute’s Justin Garcia) found that single Millennials were 66 percent less likely than members of older generations to enjoy receiving oral sex. Which doesn’t bode particularly well for female pleasure: Among partnered sex acts, cunnilingus is one of the surest ways for women to have orgasms.

Ian Kerner, the New York sex therapist, told me that he works with a lot of men who would like to perform oral sex but are rebuffed by their partner. “I know the stereotype is often that men are the ones who don’t want to perform it, but I find the reverse,” he said. “A lot of women will say when I’m talking to them privately, ‘I just can’t believe that a guy wants to be down there, likes to do that. It’s the ugliest part of my body.’ ” When I asked 20-somethings about oral sex, a pretty sizable minority of women sounded a similar note. “Receiving makes me nervous. It feels more intimate than penetration,” wrote one woman. “I become so self-conscious and find it difficult to enjoy,” wrote another.

Mendelsund / Munday

Over the past 20 years, the way sex researchers think about desire and arousal has broadened from an initially narrow focus on stimulus to one that sees inhibition as equally, if not more, important. (The term inhibition, for these purposes, means anything that interferes with or prevents arousal, ranging from poor self-image to distractedness.) In her book Come as You Are, Emily Nagoski, who trained at the Kinsey Institute, compares the brain’s excitement system to the gas pedal in a car, and its inhibition system to the brakes. The first turns you on; the second turns you off. For many people, research suggests, the brakes are more sensitive than the accelerator.

That turn-offs matter more than turn-ons may sound commonsensical, but in fact, this insight is at odds with most popular views of sexual problems. When people talk about addressing a lack of desire, they tend to focus on fuel, or stimulation—erotica, Viagra, the K‑Y Jelly they were handing out at the New Brunswick student-health center. These things are helpful to many people in many cases, but they won’t make you want to have sex if your brakes are fully engaged.

In my interviews, inhibition seemed a constant companion to many people who’d been abstinent for a long time. Most of them described abstinence not as something they had embraced (due to religious belief, say) so much as something they’d found themselves backed into as a result of trauma, anxiety, or depression. Dispiritingly but unsurprisingly, sexual assault was invoked by many of the women who said they’d opted out of sex. The other two factors come as no great shock either: Rates of anxiety and depression have been rising among Americans for decades now, and by some accounts have risen quite sharply of late among people in their teens and 20s. Anxiety suppresses desire for most people. And, in a particularly unfortunate catch‑22, both depression and the antidepressants used to treat it can also reduce desire.

“I have a therapist and this is one of the main things we’re working on,” a 28-year-old woman I’ll call April wrote to me, by way of explaining that, owing to intense anxiety, she’d never slept with anyone or been in a relationship. “I’ve had a few kisses & gone to second base (as the kids say) and it really has never been good for me.” When we later spoke by phone, she told me that in adolescence, she’d been shy, overweight, and “very, very afraid of boys.” April isn’t asexual (she gives thanks for her Magic Bullet vibrator). She’s just terrified of intimacy. From time to time she goes on dates with men she meets through her job in the book industry or on an app, but when things get physical, she panics. “I jumped out of someone’s car once to avoid him kissing me,” she said miserably. As we were ending the conversation, she mentioned to me a story by the British writer Helen Oyeyemi, which describes an author of romance novels who is secretly a virgin. “She doesn’t have anyone, and she’s just stuck. It’s kind of a fairy tale—she lives in the garret of a large, old house, writing these romantic stories over and over, but nothing ever happens for her. I think about her all the time.”

In exchanges like these, I was struck by what a paralyzing and vicious cycle unhappiness and abstinence can be. The data show that having sex makes people happier (up to a point, at least; for those in relationships, more than once a week doesn’t seem to bring an additional happiness bump). Yet unhappiness inhibits desire, in the process denying people who are starved of joy one of its potential sources. Are rising rates of unhappiness contributing to the sex recession? Almost certainly. But mightn’t a decline in sex and intimacy also be leading to unhappiness?

Moreover, what research we have on sexually inactive adults suggests that, for those who desire a sex life, there may be such a thing as waiting too long. Among people who are sexually inexperienced at age 18, about 80 percent will become sexually active by the time they are 25. But those who haven’t gained sexual experience by their mid-20s are much less likely to ever do so. The authors of a 2009 study in The Journal of Sexual Medicine speculated that “if a man or woman has not had intercourse by age 25, there is a reasonable chance [he or she] will remain a virgin at least until age 45.” Research by Stanford’s Michael Rosenfeld confirms that, in adulthood, true singledom is a far more stable category than most of us have imagined. Over the course of a year, he reports, only 50 percent of heterosexual single women in their 20s go on any dates—and older women are even less likely to do so.

Other sources of sexual inhibition speak distinctly to the way we live today. For example, sleep deprivation strongly suppresses desire—and sleep quality is imperiled by now-common practices like checking one’s phone overnight. (For women, getting an extra hour of sleep predicts a 14 percent greater likelihood of having sex the next day.) In her new book, Better Sex Through Mindfulness, Lori Brotto, an obstetrics-and-gynecology professor at the University of British Columbia, reviews lab research showing that background distraction of the sort we’re all swimming in now likewise dampens arousal, in both men and women.

How can such little things—a bad night’s sleep, low-grade distraction—defeat something as fundamental as sex? One answer, which I heard from a few quarters, is that our sexual appetites are meant to be easily extinguished. The human race needs sex, but individual humans don’t.

Among the contradictions of our time is this: We live in unprecedented physical safety, and yet something about modern life, very recent modern life, has triggered in many of us autonomic responses associated with danger—anxiety, constant scanning of our surroundings, fitful sleep. Under these circumstances, survival trumps desire. As Emily Nagoski likes to point out, nobody ever died of sexlessness: “We can starve to death, die of dehydration, even die of sleep deprivation. But nobody ever died of not being able to get laid.”

When Toys “R” Us announced this spring—after saying it had been struggling because of falling birth rates—that it would be shutting down, some observers mordantly remarked that it could be added to the list of things that Millennials had destroyed.

Societal changes have a way of inspiring generational pessimism. Other writers, examining the same data I’ve looked at, have produced fretful articles about the future; critics have accused them of stoking panic. And yet there are real causes for concern. One can quibble—if one cares to—about exactly why a particular toy retailer failed. But there’s no escaping that the American birth rate has been falling for a decade.

At first, the drop was attributed to the Great Recession, and then to the possibility that Millennial women were delaying motherhood rather than forgoing it. But a more fundamental change may be under way. In 2017, the U.S. birth rate hit a record low for a second year running. Birth rates are declining among women in their 30s—the age at which everyone supposed more Millennials would start families. As a result, some 500,000 fewer American babies were born in 2017 than in 2007, even though more women were of prime childbearing age. Over the same period, the number of children the average American woman is expected to have fell from 2.1 (the so-called replacement rate, or fertility level required to sustain population levels without immigration) to 1.76. If this trend does not reverse, the long-term demographic and fiscal implications will be significant.

A more immediate concern involves the political consequences of loneliness and alienation. Take for example the online hate and real-life violence waged by the so-called incels—men who claim to be “involuntarily celibate.” Their grievances, which are illegitimate and vile, offer a timely reminder that isolated young people are vulnerable to extremism of every sort. See also the populist discontent roiling Europe, driven in part by adults who have so far failed to achieve the milestones of adulthood: In Italy, half of 25-to-34-year-olds now live with their parents.

When I began working on this story, I expected that these big-picture issues might figure prominently within it. I was pretty sure I’d hear lots of worry about economic insecurity and other contributors to a generally precarious future. I also imagined, more hopefully, a fairly lengthy inquiry into the benefits of loosening social conventions, and of less couple-centric pathways to a happy life. But these expectations have mostly fallen to the side, and my concerns have become more basic.

Humans’ sexual behavior is one of the things that distinguish us from other species: Unlike most apes, and indeed most animals, humans have sex at times and in configurations that make conception not just unlikely but impossible (during pregnancy, menopause, and other infertile periods; with same-sex partners; using body parts that have never issued babies and never will). As a species, we are “bizarre in our nearly continuous practice of sex,” writes the UCLA professor Jared Diamond, who has studied the evolution of human sexuality. “Along with posture and brain size, sexuality completes the trinity of the decisive aspects in which the ancestors of humans and great apes diverged.” True, nobody ever died of not getting laid, but getting laid has proved adaptive over millions of years: We do it because it is fun, because it bonds us to one another, because it makes us happy.

A fulfilling sex life is not necessary for a good life, of course, but lots of research confirms that it contributes to one. Having sex is associated not only with happiness, but with a slew of other health benefits. The relationship between sex and wellness, perhaps unsurprisingly, goes both ways: The better off you are, the better off your sex life is, and vice versa. Unfortunately, the converse is true as well. Not having a partner—sexual or romantic—can be both a cause and an effect of discontent. Moreover, as American social institutions have withered, having a life partner has become a stronger predictor than ever of well-being.

Like economic recessions, the sex recession will probably play out in ways that are uneven and unfair. Those who have many things going for them already—looks, money, psychological resilience, strong social networks—continue to be well positioned to find love and have good sex and, if they so desire, become parents. But intimacy may grow more elusive to those who are on less steady footing.

When, over the course of my reporting, people in their 20s shared with me their hopes and fears and inhibitions, I sometimes felt pangs of recognition. Just as often, though, I was taken aback by what seemed like heartbreaking changes in the way many people were relating—or not relating—to one another. I am not so very much older than the people I talked with for this story, and yet I frequently had the sense of being from a different time.

Sex seems more fraught now. This problem has no single source; the world has changed in so many ways, so quickly. In time, maybe, we will rethink some things: The abysmal state of sex education, which was once a joke but is now, in the age of porn, a disgrace. The dysfunctional relationships so many of us have with our phones and social media, to the detriment of our relationships with humans. Efforts to “protect” teenagers from most everything, including romance, leaving them ill-equipped for both the miseries and the joys of adulthood.

In October, as I was finishing this article, I spoke once more with April, the woman who took comfort in the short story about the romance novelist who was secretly a virgin. She told me that, since we’d last talked, she’d met a man on Tinder whom she really liked. They’d gone on several dates over the summer, and fooled around quite a bit. As terrified as she had been about getting physically and emotionally intimate with another person, she found, to her surprise, that she loved it: “I never thought I would feel that comfortable with someone. It was so much better than I thought it was going to be.”

As things progressed, April figured that, in the name of real intimacy, she should explain to the man that she hadn’t yet had sex. The revelation didn’t go over well. “I told him I was a virgin. And he broke up with me. Beforehand, I figured that was the worst thing that could happen. And then it happened. The worst thing happened.” She paused, and when she spoke again her voice was steadier and more assured. “But I’m still here.”