panacea that many thought they would be. Networks in Telecommunications Tariffing also affects the transaction costs faced by customers. The filed-rate doctrine dictates that the tariff defines the entirety of the network-customer rela- tionship. Any deviations from the tariff are preempted, even when both parties agree to alternative terms. This means that customers cannot rely on the repre- sentations of the carrier regarding the terms of service and instead must verify the terms of services published in the tariffs. In recent years, regulatory authorities have relaxed this restriction and allowed carriers to petition for waivers that allow them offer more customized services. Whether on balance the transaction costs of negotiating terms of service will exceed or fall short of the cost of verifying the tariff terms is an empirical question. Indeed, the uniformity of application man- dated by tariffs effectively prevents networks from customizing solutions to the needs of particular customers. Furthermore, although networks are permitted to impose supply-side price discrimination by imposing price differentials that are cost-justified, tariffs prevent networks from mitigating the effects of nonmarginal cost pricing necessitated by the presence flarge fixed costs by engaging in demand- side price discrimination through regimes such as Ramsey pricing. Imposing retail access thus creates significant transaction costs that would not otherwise exist. These costs must be included in any assessment of the efficiency of imposing retail access. 2. Wholesale Access Wholesale access compels network firms to permit their competitors to act as distributors that perform the merchant activities needed to procure the network services and resell them to final customers. A critical way to determine whether wholesale access is economically efficient is to examine the types of transaction costs that are associated with it. Under the classic Coasian theory of the firm, a function will be brought within the boundary of the firm whene