Are the Uber and Lyft Bubbles about to Burst?

One of my favorite things to ask rideshare drivers is whether and how they calculate their earnings: Do they keep track of hourly wages, how important are incentive bonuses, how do they maximize fuel efficiency and minimize expensive wear on their car, etc. The answers vary wildly, as do the reasons that people drive. Some do only infrequently, as a way to make extra money; some drive as a placeholder in between jobs; some drive more or less full-time (setting their own hours, of course).

Unsurprisingly, those who drive the...