For a happy marriage, everyone needs to feel like they're contributing. Flickr / Ray Dumas If we needed another argument for equitable marriage, that argument is here.

According to a new study, published in this month's "American Sociological Review," the less money you earn relative to your spouse, the more likely you are to cheat on them — and the chances go up even more if you're entirely financially dependent.

While that's true for both genders, it's more true of economically dependent men: 15% of men who are completely financially dependent on their wives cheat, compared to 5% of women in the same boat.

"We naturally compare ourselves to our partners," explains Christin Munsch, an associate professor of sociology at the University of Connecticut and the author of the study. "It's what we do. And you don't want to feel like you're always coming out on the losing end of the comparison."

But while nobody likes feeling like they're losing — and the stats seem to back that up — there's "something about men and masculinity that makes men particularly uncomfortable when they're economically dependent." When there's a significant earning disparity, women are a little bit more likely to cheat; men are a lot more likely to cheat.

Those men, she argues, may feel emasculated when they're not living up to their societally prescribed role as primary earner — and accordingly, they're more likely to seek validation of their masculinity elsewhere.

That's consistent with what career expert Nicole Williams has seen in her own practice. "I definitely see these men feeling slightly threatened," she says. "And in some cases, the result of that is actual cheating." An affair is a way for those threatened men to "reestablish masculinity," Munsch observes, while simultaneously "distancing themselves from the source of their threat: their breadwinning spouse."

Though gender norms may be changing, assumptions about masculinity seem to be alive and well and living in the US. Munsch was working with a particularly young data set — American heterosexual married people between the ages of 18 and 32.

"Even though they're going to universities with just as many women, and these women are getting jobs that are on par with the kind of jobs they're getting," the expectation that they'll someday be the primary breadwinners pervades.

If you look at who's least likely to cheat, the gender plot thickens: when women are the primary earners in their relationships, they actually tend to be more faithful — a noteworthy finding, Munsch points out, given that high powered women likely have more opportunities for affairs, as well as more disposable income to cover them up. (The same cannot be said of high earning men: when they bring in more than 70% of the household income, their cheating rates go up again.)

By staying faithful, she suggests in the paper, female breadwinners are trying to "counteract their own gender deviance, validate their husbands' masculinity, and safeguard their relationships."

Like financially dependent men who cheat to reinforce their manliness, breadwinning women seem to be extra-faithful to reinforce their status as good wives. (Williams, who notes that a lot of high-earning women are both primary breadwinners and do the bulk of the childcare, has her own analysis: "they don't have time to cheat, let's be honest.")

So what does this all mean? Munsch stresses that the takeaway is not that women should necessarily take low-paying jobs and men should be primary breadwinners and we should all live in red brick houses with white picket fences — far from it.

"If you were to look at which type of couple has the lowest probability of cheating for either partner, it's going to be the equal earners — those men and women who make the same amount of money have a 3.4% predicted probability of cheating." In general, we like being in "equal, stable relationships where both partners contribute."

Instead, the study suggests that traditional gender expectations still exert a damaging amount of control on our lives, and a wider range of what Munsch calls "acceptable roles and responsibilities" would behoove us all — and all of our marriages.

One way to help facilitate that? Build a more equitable workplace.

It's true that "infidelity prevention" is hardly the main argument for closing the wage gap, overcoming motherhood bias, and instituting family-friendly policies — but keeping women in the workforce, and making sure they're earning at full potential, would "inherently be good for relationships and relationship stability," Munsch says.