Here's how much more money you could make just from joining a frat

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Joining a fraternity can cost you over $1,000 extra dollars a year in college, but odds are that you could end up seeing a return on that investment.

In a paper titled "Social Animal House: The Economic and Academic Consequences of Fraternity Membership," researchers from Union College found that going Greek raises your income by 36 percent down the line. The academic cost, meanwhile, is a small one: a 0.25 point drop in GPA on the traditional 4-point-scale.

In other words, you might graduate with a 2.75 GPA while your classmate who didn't pledge ends up with a 3.00. But if he makes $75,000 a year, you could expect to make $102,000.

"These results suggest that fraternity membership causally produces large gains in social capital, which more than outweigh its negative effects on human capital," the researchers write.

This is not necessarily the case at every college, though, economist Stephen Schmidt, one of the authors of the paper, tells CNBC Make It. He and his colleagues surveyed alumni aged 25 to 65 from only one small, undisclosed Northeastern liberal arts school. Extrapolating to say that their findings hold true no matter the size, academic strength and fraternity culture of a school, would be speculative, he says.

But the researchers do feel comfortable saying that, at this school, being a member of a frat is what caused certain men to earn more later in life. "We've used an analytical technique that lets us get at the question of: 'Is this a causal relationship?'" says Schmidt.

He wanted to make sure the membership was what made the difference. After all, it could be that the same kind of kid who joins a frat also tends to be interested in majoring in business, which often leads to a high-paying position. Or it could be that the students from the middle and upper classes, who tend to go on to make a lot of money as adults regardless of their college experience, are more likely to join fraternities in the first place.

But Schmidt and his colleagues controlled for these other confounding influences involved using "instrumental variables," or ones that are independent of personal characteristics. In the end, they felt confident that fraternity membership could actually get credit for boosting income later.

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Notably, the researchers did not find the same effect for sororities. Schmidt believes that was the case because the school he studied was not always coed, so there is not as large of a sorority network available for sisters to use as a career resource.

And the community of people who can help you later in life is key to earning more, Schmidt and his colleagues think. Such a network might "discriminate in your favor," he says.

Overall, that community is one of four things researchers believe give Greeks a boost.

In addition to access to a network, you could benefit from the enhancement of "soft" skills, your ability to socialize professionally, and peer influences "that push people into relatively high-paying professions." What that means, Schmidt explains, is that you might be more likely to study finance if that's what many of your fraternity brothers are doing.

So even if you join a frat at a very different kind of school, for these four reasons you could be rewarded for it later, their research suggests.

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