ese scholars argue that by the time of the breakup of AT&T, fiber optics had replaced microwave as the primary technology for long- distance transmission. Because fiber optics is essentially a wireline technology, long distance once again bore the natural monopoly characteristics (MacAvoy and Robinson 1983; Huber 1993; MacAvoy 1996). 26 The Court of Appeals affirmed this order in relevant part (Nat'l Ass'n of Regulatory Util. Comm'rs V. FCC, 737 F.2d 1095 (D.C. Cir. 1984)). The Regulation of Local Telephone Networks the concern that emerged as the most important was that the capital needed to establish long-distance service might impede new entrants from offering nationwide service from the outset, which in turn made it more difficult for new entrants to compete with AT&T. The FCC therefore imposed regulations providing new entrants with access to portions of AT&T's network to fill in the transitional coverage gaps that existed as they built out their networks, in the hope that new entrants would use access as a stepping stone to true facilities-based competition (FCC 1980c). Congress, the FCC, and the Supreme Court also invoked this rationale to justify the provisions of the 1996 Act mandating access to local telephone networks (U.S. House 1996; FCC 1996a; Verizon, 535 U.S. at 491-92). As we discussed in earlier chapters, access requirements can be quite problem- atic from the standpoint of both dynamic efficiency and administrability. As Justice Breyer noted in his partial concurrence and dissent in Iowa Utilities Board: [A] sharing requirement may diminish the original owner's incentive to keep up or to improve the property by depriving the owner of the fruits of value- creating investment, research, or labor. [One cannot] guarantee that firms will undertake the investment necessary to produce complex technological innovations knowing that any competitive advantage deriving from those innovations will be dissipated by the sharing requirement. (Iowa Utils. Bd., 525 U.S. at 428-29) Justice Breyer similarly noted