Why are millennials putting off marriage? Is it dating apps or the economy?

"I can't even imagine paying for a wedding right now," 26-year-old Kaitlyn Schaefer tells me. The grad student splits her time between teaching special education kids and running to class, all while accumulating tens of thousands of dollars in student debt. Oh, did I mention she just celebrated her 10th anniversary with her boyfriend? But no, marriage isn't on the table at the moment.

For many young people across the country, putting off marriage - or even settling down with a partner long term - has become the norm. The average age for first marriage is 27 for women and 29 for men; in urban areas such as New York and Washington, those averages are higher. It seems that everyone has a different answer for why: Blame it on the economy. Or dating apps. Or women's ability to delay childbearing.

But the less sexy answer is that it's all of the above.

"When there's rough economic times, marriage rates go down," explains Eric Klinenberg, sociologist and co-author of Aziz Ansari's "Modern Romance: An Investigation." "People don't feel comfortable committing to someone during hardships."

Marriage is indeed a financial investment, which explains why people in their 20s aren't ready to take the plunge, considering the mounting debts and scarce job prospects they face today.

"We both have student debt, so it's ridiculous," Schaefer said. "And it's a domino effect. Because then what's the next step? Kids? A house? We can't afford that now."

Shaky finances can keep millennials from tying the knot, even into their 30s. James Fay, a 33-year-old who works in advertising says he and his ex never made it down the aisle because they were still establishing themselves professionally. "We didn't have our careers established to the point where we thought it was smart to have a wedding and settle down and all that. Now that I'm single again, marriage isn't off the table and my career now is further along, so it's an easier choice."

It's not all bad news, economically. For women, marriage is less of a financial necessity. "There a couple of reasons why people choose to get married," says Andrew Zuppann, assistant professor of economics at the University of Houston. " One is to have two people in the household to share the housework and finances. A big change between 2016 and 1950 is that a lot less people rely on this and have opportunities to afford to be on their own."

We're also better able to delay parenthood. "Contraceptives and abortion are letting women put off pregnancy and marriage longer," Zuppann said. "In general, the reasons why marriage age is much later now are: birth control, technology, abortion, changes in female pay and household technology, like appliances."

Fair enough, but what about the effect of internet dating? According to the Pew Research Center, 15 percent of Americans use dating apps these days, a threefold increase for young people since 2013. Surely the rise of "hookup culture" is contributing to the number of singles who prefer perpetual use of Tinder and OkCupid, among others, to settling down with a long-term partner.

"The dating culture has changed. There's been a fundamental shift in the way people meet and find romance. Or even the way people in relationships communicate, due to technology," says Klinenberg, who stressed that dating apps don't keep people single forever, but that "they can keep you very busy when you're single."

"People who are on the fence are probably being swayed to delay marriage or settling down due to dating apps," says Fay, who has recently downloaded Tinder and Bumble to get back in the game. "Dating apps are the thing that single people have been waiting for since the dawn of time."

And then there are those who aren't just delaying marriage; they're not interested in it at all. Holly Dembinski, who's 28, says that after years of pursuing different relationships, being indefinitely single means "you're choosing happiness."

Klinenberg agrees. "People don't see marriage as necessary for a good life," he says. "There used to be one clear path to happiness, with strong moral expectations and having children. Now there are all kinds of legitimate choices."

"I've dated people because I just enjoyed dating them during that time. I knew that I wasn't gonna marry them, necessarily," Dembinski says. "I think realizing that you don't need to have an endgame, that there isn't a bottom line, per say, is important. There isn't a goal to pertain to be happy, it's finding happiness in the present."