But in the past five decades, more and more women have become breadwinners, at least in the U.S. Between 1960 and 2011, the proportion of two-parent U.S. households in which the mother earned all or most of the income roughly quadrupled. And in 1977, 34 percent of General Social Survey respondents rejected the idea that men should work and women should stay at home, but this figure was 64 percent in 2010.

Some researchers have speculated about why, even in light of these big-picture changes, the expectation to pay for dates falls to men. “As social roles start to change, people often embrace the changes that make their lives easier, but resist the changes that make their lives more difficult,” David Frederick, a professor of psychology at Chapman University, told The Huffington Post last summer. “Who pays for dates … is one arena where women may be resisting gender changes more than men,” he suggested.

Last year, Frederick co-authored a study larger than NerdWallet’s—one that reached about 17,000 people—which also found that men tend to pay for dates. In the study, he and his co-authors called paying for dates “a rare case” in which women are incentivized not to fight old-school gender dynamics. This same logic might explain why men who are okay stepping down as breadwinners aren’t as eager to step up to the demands of parenting and homemaking. (The scope of Frederick’s study was wider than NerdWallet’s too, and, interestingly, 39 percent of its female respondents admitted that they hoped men would reject their offers to help pay.)

Who’s expected to pay for a date may seem trivial—some would even argue that covering the tab is a form of respecting women—but there’s reason to believe that this minor, “benevolent” form of sexism can lead to a fraught question of what the man is then owed.

A 1985 study published in Psychology of Women Quarterly presented subjects with a variety of fictional dating scenarios—mixing up who invited whom, who paid, and the venue—and asked them to evaluate the acceptability of the sexual encounter that followed. Disturbingly, they found that money contorted men’s opinions of sexual consent. “Rape was rated as more justifiable,” the authors wrote, “when the man paid all the dating expenses rather than splitting the costs with the woman.” Culturally speaking, 1985 may seem distant, but the study's conclusion apparently hasn’t become any less relevant (or urgent): A more recent study, from 2010, found that men were more likely than women to think that sex should be expected when a man pays for an expensive date.

Through all these disconcerting findings, David Frederick still saw one data point that inspired optimism. Almost half of the men surveyed in the study he co-authored said that they would break up with a woman if she never offered to help pay the bill on a date. “In this single telling finding about dating and paying interactions, we see evidence of a sea change,” he and fellow authors wrote.