Driving for Uber seems like a pretty sweet gig. You get in your car, drive some people around, and make money. What's not to like? But apparently if you're a female driver, you won't enjoy it as much as a male one.

A new study found that female Uber drivers make seven percent less money than male drivers. The ridesharing app claims that it's algorithms are gender blind to ensure there isn't a bias. But economists examined 1.8 million drivers and found there was a gap in gender payment.

Uber and other "gig economy" jobs are believed to largely avoid traditional gender pay gap issues because they're more flexible and don't require the same structure as a traditional office job. In fact, one of the economists from the study said he hypothesized that women would actually make more from Uber than men.

“If there was a difference, I think the pay gap would slightly favor women,” said John List, chairman of the University of Chicago economics department and chief economist at Uber. “And this is kind of for two reasons. One, I knew that they had worked fewer hours per week so they had a chance to cherry-pick the better hours during the week. Point number two was, if there was discrimination on the platform, I was thinking that riders would actually prefer female drivers to male drivers.”

So why were women paid less if the algorithms are gender blind? The economists offered three possible explanations. One was experience. Uber drivers who made more than 2,500 trips tended to make $3 per hour more than lesser experience drivers. And men tend to drive more for Uber than women. Another explanation was speed. According to their data, men tended to drive 2.2 percent faster than women, and that resulted in a slightly higher increase in income. And the third explanation was location. Men tended to drive in areas with higher surge charges and lower wait times than women drivers.

Another interesting note is that 77 percent of female drivers quit after less than six months of working with Uber compared to only 65 percent of men.

(h/t Fortune)