At one corner of the internet, survey reports and feature stories suggest millennials, the generation known for delaying adulthood, predominantly opt for pets rather than children. But in another, data on millennials’ childbearing tendencies paint a different picture — one with serious financial consequences if the parents aren’t careful planners, especially for a generation already struggling under the weight of student debt.

Public acceptance of out-of-wedlock births reached a record high of 62 percent, and 68 percent of millennials, last year, compared to 45 percent in 2002, according to research from Gallup. With that acceptance comes a prevalence of unmarried millennials with children: Gallup also found that close to half of the oldest millennials, or those age 34, are having kids without exchanging vows, compared to just 30 percent of Gen Xers in 2000, when members of that cohort were between the ages of 30 and 34.

Read: Millennials Are Splitting Into Haves And Have Nots

According to an analysis of government data by the American Enterprise Institute, a conservative think tank, 55 percent of today’s 28- to 34-year-olds with kids put childbearing ahead of marriage. That’s more than double the quarter of younger Baby Boomers who could say the same between the mid-1980s and late 1990s, when they reached that age range. A third of older millennials overall, AEI also noted, had children outside of or before marriage, compared to a fifth of Baby Boomers upon reaching the same age.

W. Bradford Wilcox, a professor of sociology at the University of Virginia and one of the authors of the AEI report, said the phenomenon stemmed from a confluence of social and economic changes.

“Liberals will stress economic factors and conservatives will stress cultural factors,” he said. But while “the economic circumstances make millennials take longer to establish stable careers,” the same pattern of out-of-wedlock births was not quite present among young people in the wake of the Great Depression.

Other demographic trends point to a generation of older, more financially stable and deliberate parents, married or not, even as a growing portion of Americans are delaying or avoiding matrimony. Birth rates among teens and 20-somethings, for example, have dropped off and those of 30- and 40-somethings have risen in the past decade, while women have come to dominate their male counterparts in terms of postsecondary degree attainment and have increased their workforce participation to nearly 60 percent from below half over the past several decades. Meanwhile, the rate of unwanted pregnancies across the U.S. generally fell in the first decade of the new millennium, and the nationwide abortion rate is at its lowest since Roe v. Wade, according to the Guttmacher Institute.

But millennials make less than Baby Boomers did at their age, and those in their early 30s, who are becoming increasingly more likely to have children than younger members of the generation, will continue to endure the long-term consequences of entering an economy stunted by the 2008 financial crisis.

“The millennials who graduated from college in 2009 — they were really held back by the Great Recession,” Dowell Myers, a demography professor at the University of Southern California’s Price School of Public Policy, told IBT. Though younger millennial graduates are entering a much more favorable job market, he added, the older members of the generation “won’t all get back on track.”

Read: Young Workers Are Most Likely To Have Secondary Income

The trend is magnified among those without postsecondary education, Wilcox noted.

“Both marriage and fertility have been postponed in recent years, but for millennials who’ve forgone a college degree, they’ve postponed or foregone marriage more than they’ve postponed or foregone childbirth,” he said. “There’s a real dramatic divide in terms of education, as far as who’s having kids without getting married among millennials.”

Those without degrees typically aren’t the best planners, according to Wilcox, which likely adds to a more widespread problem of foresight associated with childbearing. Namely, Americans’ expectations of the costs of raising a child also tend to fall far out of touch with the reality. The personal finance site NerdWallet, for instance, calculated that households making $200,000 annually would likely spend around $52,000 on their child's first year of life, while those with incomes of $40,000 would spend about $21,000. NerdWallet then surveyed hopeful parents on how much they believed the first year of the average baby would cost and found that 54 percent expected to spend $5,000 or less, and only 11 percent thought they’d have to fork over more than $15,000.

Proponents of the marriage-first model, including the Wilcox, often point to Brookings Institution senior fellow Ron Haskins’ so-called “success sequence,” which entails graduating from high school, obtaining a job or finding a partner who has one and, if the individuals want a child, waiting until after marriage and their 21st birthdays to do so. By following these simple steps, Haskins maintains, young Americans have a very low chance of ending up in poverty. (It’s worth noting, however, that when people of different races follow these same norms, the outcomes are substantially unequal and in favor of whites.)

Regardless, Wilcox stressed that, even with elevated divorce rates, the legal — in addition to, of course, the romantic — sanctity of marriage ensures worthwhile financial benefits.

“I do think that cohabitating couples realize that marriage is more than just a relationship,” he said. “For the average couple, your odds of making it are kind of higher than if you’re simply cohabitated.”