Market Structure and Congestion Externalities: Theory and application to the ride-hailing industry
Gomez Gelvez, Julian Andres
Williams III, Roberton C
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The encompassing theme of this dissertation is the analysis of markets that feature market power and negative externalities. I focus mainly on congestion externalities, as externalities that affect only market participants. The first chapter evaluates the efficiency of private pricing of congestible resources. I develop a model of congestible resource use that explicitly considers a bivariate distribution of reservation values and sensitivities to congestion across potential users. This model highlights the importance of the correlation between reservation values and sensitivities to congestion to judge the efficiency of private pricing. Numerical results based on a road pricing example show that monopolistic pricing can range from very inefficient (price too high) when the correlation is negative to almost complete efficiency when it is strong and positive. The second chapter studies ride-hailing markets mediated by digital platforms like Uber. I extend the model of the first chapter to include a supply side of drivers. A monopolistic platform chooses prices on both sides of the market to maximize profit. I calibrate the model to the morning peak period of Bogota, Colombia. The results show that the price gap imposed by a monopolistic platform corresponds to about two thirds of the net marginal external cost caused by an additional ride hailer. A congestion charge on ride hailing is then justified. However, the optimal congestioncharge, as a tax on the price charged to riders, covers only 50% of the marginal external cost. The last chapter explores the effects of modifying several assumptions of the ride-hailing model developed in the second chapter. The main modification is to move from a monopolistic market structure to a duopoly. I show that absent any differentiation between platforms, competition leads to zero profits. This result supports the idea that ride-hailing markets gravitate towards a single platform. Assuming a small amount of differentiation, the duopoly equilibrium reduces the price charged to riders and increases the size of the market. This expansion reduces overall welfare due to the external effect on traffic congestion and calls for a higher congestion charge.