Oh, I forgot about rating! It indeed should act in the same way as tipping, but not necessarily to the same degree. It's possible, for instance, that the change

Oh, I forgot about rating! It indeed should act in the same way as tipping, but not necessarily to the same degree. It's possible, for instance, that the change on a the driver's earnings conditional on any new rating is lower than the tip that he'd get from a new trip. Even more so as a driver's rating is the average rating from all his recent trips. If pulls a 5-star service for 499 customers and a 0-star service for a single customer (for whatever reason) his rating drops from 5 to 4.99, which doesn't seem that relevant. Unless a 0.01 drop in his rating means a loss in earnings greater than that of a lost tip, the tipping system would provide better rewards for not dropping the ball. Forgot about the social pressure, too (I'm not American). That could be a real issue, because if people don't actually consider not tipping then it's just dead as a incentive scheme. They'd have to make tipping anonymous. By the way, I don't think pressure under anonymous choice is "social". You could attribute it to education and thus society and some way but ... that's rather roundabout. I think the more appropriate term is "consciousness".