From an Uber rider’s perspective, Keith says, a round number surge like two times looks like the company is just slapping on a higher price tag because it’s raining. But when it’s 2.1 times as much, we think there must be a complex algorithm (which there is) coming up with that figure. The ride, then, is surely worth 2.1 times as much.

Source : Keith Chen Is Uber’s Head Of Economics And Decides When Uber Surges Price : NPR