Another study by Hall, Kendrick, and Nosko explores what would happen when Uber surge pricing doesn't exist, by exploiting a natural experiment caused by a surge outage on New Year's Eve during a period of high demand. They concluded that:
"we saw that in the absence of surge pricing, key indicators
of the health of the marketplace deteriorated dramatically. Drivers were likely less attracted to
the platform while, at the same time, riders requested rides in increasing numbers because the
price mechanism was not forcing them to make the proper economic tradeoff between the true
availability of driver partners and an alternative transportation option. Because of these
problems, completion rates fell dramatically and wait times increased, causing a failure of the
system from an economic efficiency perspective."
More info on Uber's blog. Thanks to Val Lee for the link!