Incentives for discrimination when upstream monopolists participate in downstream markets

A regulated upstream monopolist supplies an essential input to firms in a downstream market. If an upstream monopolist vertically integrates downstream, non-price discrimination becomes a concern. Discrimination always arises in equilibrium when the vertically integrated provider (VIP) is no less efficient than its rivals in the downstream market, but it does not always arise when the VIP is less efficient than its rivals. Numerical simulations that parameterize the regulator's ability to monitor discrimination in the case of long-distance telephone service in the U.S. reveal that pronounced efficiency differentials are required for the incentive to discriminate not to arise in equilibrium.