Have you ever given an Uber driver five stars who didn’t deserve it? If you’ve ever taken any ride-hailing service, the answer is probably yes.

Uber asks riders to give their drivers a rating of one to five stars at the end of each trip. But very few people make use of this full scale. That’s because it’s common knowledge among Uber’s users that drivers need to maintain a certain minimum rating to work, and that leaving anything less than five stars could jeopardize their status.