The growth of ride-sharing services such as Uber and Lyft has generated much discussion in the news. Drivers operate as independent businesses, working as many hours as they choose and earning a portion of the fares. Fares are set by the company, with market prices increasing during periods of high demand, such as "surge" pricing by Uber. From the driver's perspective, ride-sharing companies share many characteristics with perfectly competitive firms. Which of the following is not a characteristic found in ride-sharing companies? The short-run supply curve is nonexistent. Drivers do not have control of the prices. Supply is determined by the marginal cost incurred by each driver. Drivers face few barriers to entry.