Because the fertility rate subtly shapes many major issues of the day — including immigration, education, housing, the labor supply, the social safety net and support for working families — there’s a lot of concern about why today’s young adults aren’t having as many children. So we asked them.

Wanting more leisure time and personal freedom; not having a partner yet; not being able to afford child-care costs — these were the top reasons young adults gave for not wanting or not being sure they wanted children, according to a new survey conducted by Morning Consult for The New York Times.

About a quarter of the respondents who had children or planned to said they had fewer or expected to have fewer than they wanted. The largest shares said they delayed or stopped having children because of concerns about having enough time or money.

The survey, one of the most comprehensive explorations of the reasons that adults are having fewer children, tells a story that is partly about greater gender equality. Women have more agency over their lives, and many feel that motherhood has become more of a choice.

But it’s also a story of economic insecurity. Young people have record student debt, many graduated in a recession and many can’t afford homes — all as parenthood has become more expensive. Women in particular pay an earnings penalty for having children.

“We want to invest more in each child to give them the best opportunities to compete in an increasingly unequal environment,” said Philip Cohen, a sociologist at the University of Maryland who studies families and has written about fertility.

At the same time, he said, “There is no getting around the fact that the relationship between gender equality and fertility is very strong: There are no high-fertility countries that are gender equal.”

The vast majority of women in the United States still have children. But the most commonly used measure of fertility, the number of births for every 1,000 women of childbearing age, was 60.2 last year, a record low. The total fertility rate — which estimates how many children women will have based on current patterns — is down to 1.8, below the replacement level in developed countries of 2.1.

The United States seems to have almost caught up with most of the rest of the industrialized world’s low fertility rates. It used to have higher fertility for reasons like more teenage pregnancies, more unintended pregnancies and high fertility among Hispanic immigrants. But those trends have recently reversed, in part because of increased use of long-acting birth control methods like IU Ds.

In the Morning Consult and Times survey, more than half of the 1,858 respondents — a nationally representative sample of men and women ages 20 to 45 — said they planned to have fewer children than their parents. About half were already parents. Of those who weren’t, 42 percent said they wanted children, 24 percent said they did not and 34 percent said they weren’t sure.

One of the biggest factors was personal: having no desire for children and wanting more leisure time, a pattern that has also shown up in social science research. A quarter of poll respondents who didn’t plan to have children said one reason was they didn’t think they’d be good parents.

Jessica Boer, 26, has a long list of things she’d rather spend time doing than raising children: being with her family and her fiancé; traveling; focusing on her job as a nurse; getting a master’s degree; playing with her cats.

“My parents got married right out of high school and had me and they were miserable,” said Ms. Boer, who lives in Portage, Mich. “But now we know we have a choice.”

She said she had such high expectations for parents that she wasn’t sure she could meet them: “I would have the responsibility to raise this person into a functional and productive citizen, and some days I’m not even responsible.”

This generation, unlike the ones that came before it, is as likely as not to earn less than their parents. Among people who did not plan to have children, 23 percent said it was because they were worried about the economy. A third said they couldn’t afford child care, 24 percent said they couldn’t afford a house and 13 percent cited student debt.

Financial concerns also led people to have fewer children than what they considered to be ideal: 64 percent said it was because child care was too expensive, 43 percent said they waited too long because of financial instability and about 40 percent said it was because of a lack of paid family leave.

Women face another economic obstacle: Their careers can stall when they become mothers.

This spring, Brittany Butler, 22, became the first person in her family to graduate from college, and she will start graduate school in social work in the fall. She said it would probably be at least 10 years before she considered having children, until she could raise them in very different circumstances than in her poor hometown neighborhood in Baton Rouge, La.

She admits being “a little nervous” that it may become harder to get pregnant, but she wants to pay off her student loans and, most of all, be able to live in a safe neighborhood.

“A lot of people, especially communities of color, can’t really afford that now,” she said. “I’m just apprehensive about going back to poverty. I know how it goes, I know the effects of it, and I’m thinking, ‘Can I ever break this curse?’ I would just like to change the narrative around.”

Starting a family used to be what people did to embark on adulthood; now many say they want to wait. Last year, the only age group in which the fertility rate increased was women ages 40 to 44. Delaying marriage and birth is a big reason people say they had fewer children than their ideal number: Female fertility begins significantly decreasing at age 32.

The slogan refers to a time-honored series of life events: graduating from high school (at least), getting a full-time job, and marrying before having kids (in that order). As the conservative columnist George Will wrote last year (in a piece headlined, in part, “Listen up, millennials”), “Of the several causes of descent … into the intergenerational transmission of poverty, one was paramount: family disintegration.” He called the success sequence “insurance against poverty” for young adults.

The success sequence has a powerful allure for its adherents. But just as strongly, the idea repels: A number of critics—many of whom are academics and have sturdy research to back up their position—reject it, not because following it is a bad idea, but rather because it traces a path that people already likely to succeed usually walk, as opposed to describing a technique that will lift people over systemic hurdles they face in doing so. The success sequence, trustworthy as it may sound, conveniently frames structural inequalities as matters of individual choice.

The concept of the success sequence has caught on for multiple reasons. “I think part of the appeal is it’s a fairly straightforward way of formulating a life script,” Brad Wilcox, the director of the National Marriage Project at the University of Virginia, a professor of sociology there, and the best-known advocate of the success sequence, explained. “It has some kind of connection to the way most people came up and they sort of see perennial wisdom. And I think the fact that there are three steps to follow. That is appealing.”

Stephanie Coontz, a professor of history and family studies at Evergreen State College in Olympia, Washington, the director of public education at the nonprofit Council on Contemporary Families, and the author of Marriage, a History: How Love Conquered Marriage, largely agrees with Wilcox. “It’s a 20-second sound bite anybody can agree with,” she says. “It’s advice everybody gives their kids. There’s nothing complicated about it.”

The way the success sequence rose to prominence as a prescription for poverty says a lot about the narratives that America tells itself about meritocracy and who’s deserving of “success.” As far as I’ve been able to determine, the first use of the term occurred in 2006 when the historian and writer Barbara Dafoe Whitehead and the sociologist Marline Pearson co-authored a report called “Making a Love Connection,” for the National Campaign to Prevent Teen Pregnancy, a nonpartisan sexual-health advocacy group that’s now known as Power To Decide.

Whitehead and Pearson wrote that modern teenagers “lack what earlier generations took for granted: a normative sequence for the timing of sex, marriage and parenthood.” Then they put a slogan on such a sequence and described it. Teens, they wrote, “lack knowledge of what might be called the ‘success’ sequence: Finish high school, or better still, get a college degree; wait until your twenties to marry; and have children after you marry.”

So the phrase was born. In the years since, the sequence has been modified somewhat by its promoters to graduate high school, get a full-time job, and marry before having babies, and “success” has been defined down a little to mean “stay out of poverty.”

There has long been concern over the personal economic impact of non-marital parenthood, but a notable flare-up in the debate—one that presages the present-day success-sequence campaign—was sparked by a TV plotline. In May of 1992, the TV character Murphy Brown, of the eponymously titled show, gave birth to a child. She was single, and many social conservatives were outraged; Vice President Dan Quayle condemned the plot, saying that it “mock[ed] the importance of fathers.”

Four months later, with the Murphy Brown debate still fresh, Nicholas Zill, from a think tank called Child Trends, spoke on the topic of childhood poverty in testimony before the House Subcommittee on Human Resources. He never mentioned Brown, but he nonetheless gave powerful ammunition to social conservatives. In his talk, Zill presented data showing that 45 percent of children in single-parent families lived in poverty, versus 8 percent of children in married-couple families. He talked about both individual behavior—as in, being a single parent—and structural obstacles that perpetuate childhood poverty, such as racial discrimination, high unemployment, and too-low wages.

The research played into the hands of Bill Clinton, whose White House in 1993 was pushing welfare reform and publicized Zill’s findings to support that cause. But it also played into the hands of social conservatives, who decried sex before marriage and out-of-wedlock births, and of fiscal conservatives, who wanted welfare cut or shut down. “Stop the welfare checks,” the late Charles Krauthammer wrote in a November 1993 Washington Post column. Welfare, he argued, fueled the birthing of babies to unmarried women and fostered “social breakdown.”

Twenty-five years later, the reasoning of many who embrace the success sequence is largely the same. Krauthammer’s refrain was taken up by groups and pundits arguing for abstinence-only sex education, another round of welfare reform, and programs promoting marriage: If only people would marry before having children, they’d be financially stable.⁽¹⁾ Of course, none of these conservatives ever want to promote birth control and proper sex education, unless it's for their mistresses.

For Wilcox, a self-identified conservative Catholic who has written, with concern, about “the increasingly secular cast of American society [that] has gone hand in hand with a retreat from a family-focused way of life that prioritizes marriage and parenthood,” the main agenda is marriage promotion, not government cutbacks. “It might be an excuse for embracing a kind of libertarian, limited-government approach to things,” he says, “but I look at it more as way to share with ordinary people ways to think about younger adults and teenagers and how to order their lives in ways to maximize chances of realizing at least the economic piece of the American dream.” Wilcox favors some government intervention and spending that would, in his view, support the sequence, such as wage subsidies and more support for technical training. He also supports government spending on programs that would encourage people to marry, such as the federal Healthy Marriage Initiative.

Whitehead, now retired, says promoting marriage per se wasn’t the motivation behind her work. She only wanted to provide “some normative guidance” for young people because she was concerned about children. “The marriage part for me has more to do with a secure environment for kids to grow up in families than it is advice for young people to get married,” she told me. Long-acting methods of contraception and the subsequent reduction in teen pregnancies have altered the dynamic somewhat since she coined the term, she says, making the relative value of marriage itself, outside of childbearing, more debatable. She opposes welfare cuts, especially for single mothers, and endorses maintaining the earned income tax credit (which was reduced for some families by the tax law passed last year).

Critics of the sequence within academia, like Philip Cohen, a professor of sociology at the Maryland Population Research Center at the University of Maryland, argue that government promotion of marriage doesn’t lead to more marriages. Instead, they say, many sequence enthusiasts want to restigmatize out-of-wedlock births. By doing so, they aim to put the responsibility for poverty on the impoverished just as Krauthammer implied back in the early ‘90s, thus justifying cuts in government support while ignoring the role of late-20th-century American-style capitalism in pushing families into financial insecurity.

As Coontz puts it, “the roads you take depend on the geography where you live.” She and others cite well-known impediments to following the sequence, everything from a lack of marriageable men who earn decent wages in some communities, high incarceration rates, the decline of union power, and a general feeling that there’s little point to waiting to have a child because there’s little hope for ever really improving one’s lot. In such situations, choosing to have a baby—rather than wait for the ideal, financially responsible moment that will likely never arrive—can be the more rational choice.

The ills the success sequence aims to cure are “fundamentally driven by big economic forces,” Steven Ruggles, a historian and demographer at the University of Minnesota’s Population Center, argues. In a paper called “Patriarchy, Power, and Pay: The Transformation of American Families, 1800–2015,” Ruggles wrote that out-of-wedlock births and the decline of marriage didn’t just happen because hippies preached free love or because scientists invented the birth-control pill. “There must be a source of exogenous pressure for people to reject the values with which they were raised,” he wrote. “Between 1800 and 2000, that pressure was exerted by an economic revolution.”

The revolution he refers to is actually several: the rise of wage labor in the 19th century, the post-World War II economic boom and union wages that often allowed one parent to stay home, the subsequent decline in men’s wages that accelerated during Ronald Reagan’s presidency and continues, the corresponding entry of more women into the workplace, and other macro shifts that produced the inequalities of today. “I think it is kind of ridiculous to say the reason for social problems is that people do not have good enough morals,” Ruggles says.

“I mean that talk about personal responsibility—OK,” he says, “but what about the responsibility of the institutions and the society where we used to make promises to people and now it’s a scarier world in terms of job security?”

Whitehead, who argued in a 1993 essay for The Atlantic called “Dan Quayle Was Right” that increasing numbers of step-parent and single-parent families “weakens and undermines society,” firmly agrees. Any promotion of personal responsibility and the success sequence, she says, should take a back seat to addressing the growing institutional barriers that make it difficult to raise a family out of poverty. Many now live, she says, in a society that is “every man, woman, and child for him or herself,” with a loss of institutional solidarity and the social contract. “It’s one of the tragedies of the times we’re living through.” Any debate over the success sequence pales by comparison.

Jennifer Lundquist, a sociologist at the University of Massachusetts-Amherst, lent support to this structural approach to marriage, poverty, and child bearing. When she studied marriage in the U.S. military, she found that when the economic and social structures around people were stable and equal, differences in marriage rates largely disappeared. “Black civilians are less likely than white civilians to marry, whereas black and white military enlistees exhibit similar—and very high—propensities to marry,” she wrote.⁽²⁾ As almost anyone in the military can attest, lots of people get married quickly. Both because it's a high-stress environment that fosters powerful but temporary emotional bonds; and because we literally get paid more by having a spouse and/or children than we do if we're single.

The appeal of the success sequence, then, appears to be about more than whether it’s a good idea. In a society where so much of one’s prospects are determined by birth, it makes sense that narratives pushing individual responsibility—narratives that convince the well-off that they deserve what they have—take hold. Democracy was established in part as a reaction to the notion that there should be any preset order to the world, with rich and poor, sovereign and ruled. But, especially when paired with capitalism, democracy still creates winners and losers. The resulting dissonance between the ideals of democratic life and the reality forced new explanations for inequality. “If I say, ‘All are created equal,’” Coontz says, “how can I countenance slavery, or hungry factory workers?” And if slaves are set free, and workers given new rights, “I say, ‘We have a country that no longer keeps you down, so you must be doing something wrong.’ We say, ‘Alright, the only way I can live with inequality is to see it as the fault of those who have failed to do as well as I.’” To do otherwise leads to a dangerous idea: that the system itself fosters inequality.

Kristi Williams, a sociologist at Ohio State University who studies the intersection between health and family formation, says this explains why the promotion of the success sequence comes mainly from think tanks, not academic researchers. A good experiment to test the success sequence is impossible, she explains—researchers can’t just force one group of women to have babies without marriage and a control group to wait until marriage, and then follow the families for years. But suppose it wasn’t—assume such an experiment confirmed its validity: “The question becomes, ‘Then what?’” she says. Pass a law requiring marriage?

Another limitation: The success sequence is defined recursively, in that the steps to satisfying it are also the very things that mark what’s considered a successful life. Of course one becomes successful after graduating high school, getting a good job, and marrying—those are how many Americans define success. That’s why Cohen calls it “a meme in search of a policy.” And Matt Bruenig, the founder of a think tank called the People’s Policy Project and a former National Labor Relations Board attorney, has argued that the sequence in truth amounts to just one item: Have a decent job, and you won’t live in poverty. Despite this view of the sequence as empty platitude, though, some have a strong investment in it because it is both a good blueprint for many people and it can, consciously or not, be used to justify all sorts of inequities. That makes it a very powerful bumper sticker.