y types of productive inputs are used to create network services. Networks can require considerable amounts of land for rights of way and central offices. For example, railroads, electric power transmission grids, and natural gas pipelines use land for rights of way. Second, companies employ considerable amounts of labor services to construct, operate, and maintain network facilities. Third, companies employ sub- stantial amounts of capital equipment to build the network, including heavy con- struction equipment. Capital equipment forms part of the network itself, including, for example, the lines and switches of a telecommunications network. Companies employ financial capital to finance the construction, operation, and maintenance of the network. However, land, labor, and capital are the inputs to the network, not its outputs. By attaching a local loop, say a twisted copper pair, between the network and a household, a telephone company extends the transmission services of the network to the household. The local loop is an input used to provide the transmission service inbound or outbound; it is not an output of the network. This is an important issue because regulators have classified the local loop as an unbundled network element (UNE). Telecommunications companies are asked to provide other companies with the UNE as if it were an output of the network rather than a detached input of the network. D. Access to Networks We define access to networks as the marketplace transactions between firms that provide networks and users of network services. Firms that establish networks can provide services to retail customers, wholesalers of services, suppliers of content and other complementary services, competitors, and other firms that supply network services. These transactions provide network users with access to network services. Networks in Telecommunications We introduce a classification scheme that identifies the main forms of access to networks. Our analysis of access using the classification scheme allows economi