Bounding consumer surplus by monopoly profits

Regulatory agencies and other public authorities in the United States frequently require private firms seeking regulatory approvals to enter geographic markets, or offer products, that they would not otherwise provide. Examples include “build-out” rules for cable television franchisees, and universal service or “common carrier” obligations. The social welfare consequences of such policies are often difficult to evaluate because, among other things, consumer surpluses generated by entry must be assessed. This article shows that the level of (variable) monopoly profits in the markets of interest can be used to place an upper bound on the associated consumer surplus whenever demand vanishes at a sufficiently high price. This result, which is new, can then be used to evaluate the social consequences of forced entry. Our methods can also be used to provide a bound on the change in consumer surplus resulting from the imposition of regulated prices on an existing monopoly.