tailored to their needs. We also show how access regulation can reduce economic welfare by narrowing the number of dimensions along which networks can compete. Access regulation necessarily requires network providers to interconnect with any other firm that that presents its data at a designated location in a designated format. This has the effect of freezing both the location and the format of the interface into place, a consequence that is quite problematic in industries such as communications that are undergoing rapid technological change. Access regulation also commoditizes bandwidth in ways Conclusion that narrow the number of dimensions along which firms can compete, which has the effect of preventing firms from pursuing niche or differentiation strategies that can allow them to survive notwithstanding the presence of unexhausted returns to scale. In SO doing, it forces networks to compete on price and network size, which in turn reinforces the advantages enjoyed by the largest players. Our analysis has implications for access policy generally. Granting access has become a public policy code word for mandatory access in a variety of areas that extend beyond communications. Access is an extension of the antitrust doctrine of essential facilities. Under the essential facilities doctrine, promotion of competition or remedies for anticompetitive behavior have led to mandatory access to manufac- turing and transportation facilities. Policymakers have been tempted to mandate access to assets that are less tangible, such as intellectual property and innovations. Mandatory access raises substantial legal questions. It must be emphasized that networks are privately owned facilities. The boundaries of the network are also the boundaries of ownership. Mandated access affects returns and control of the network owner. Without adequate compensation, access becomes a form of governmental taking. Equally important are concerns about investment incentives and dynamic efficiency. As the Trinko Court found, compelling telecom