Male Uber drivers earn 7 percent more per hour than female Uber drivers, based on a recent study that examined data from the ride-hailing app in Chicago.

The study, a collaboration between Uber, Stanford University and the University of Chicago, says men likely earn more from driving because they develop more experience on the platform, can choose when and where to chase lucrative fares and drive faster.

“This suggests that, as the gig economy grows and brings more flexibility in employment, women’s relatively high opportunity cost of non-paid-work time and gender-based preference differences can perpetuate a gender earnings gap even in the absence of discrimination,” according to the authors.

The findings are based on data compiled from 120,223 drivers, about 30 percent of whom are women. As a group, Chicago’s drivers racked up 33 million hours of driving from January 2015 to March 2017. They represent 6.4 percent of all active Uber drivers in the United States during that time period.

Based on the study, female Uber drivers got $20.04 per hour, or $1.24 less than men.

The study looked at the 50 areas of Chicago with the most Uber rides — though didn’t say where they were — and concluded that “men drive in the parts of Chicago where pay is higher due to factors such as higher surge and shorter waiting times.”

It also found that male drivers are more likely to be part of a group that have given over 2,500 rides. That group tends to earn more than less-experienced drivers.

Lastly, the study finds that male drivers drive 2.2 percent faster than female drivers, though like all Chicago drivers they crawl through bad traffic in the usual spots. Driving faster helps drivers earn more money.

The company said there is no evidence of outright discrimination among riders using Uber.

“This result is somewhat surprising because Uber uses a gender-blind algorithm and drivers earn according to a transparent formula based on the time and distance of trips,” the company said in a blog post.