&T's, which became some of Comcast's better cable plant. RCN was expanding into numerous major markets that had a large number of homes passed, but it was not appar- ently focused on the bottom line. Overbuilding is not a guaranteed failure. Under proper circumstances, especially on a small scale, an overbuilder can achieve some success. And costs have fallen substantially since the boom, as the supply and demand equilibrium has changed for both materials and labor. Many current overbuilders are municipally owned electric utilities that add cable or even fiber to the home to their product mix. They are often motivated by economic development goals-superior telecommunications, they suggest, can help attract industry and bring other benefits to the population. This often works best in small towns that have been neglected by large incumbents. But overbuilding cannot be counted on as a general approach to bring down telecommunications rates. Whether aimed at residents and leading with video programming, or aimed at business and leading with fiber, overbuilders have a high burden to overcome the natural monopoly benefits that accrue to incumbents. Endnotes Rate of return is calculated in terms of profit as a percentage of the total rate base, the undepreciated value of the company's cumulative investment. Garfinkel, S., "Where Streams Converge," HotWired, Sept. 11, 1996, http://hot- wired.wired.com/packet/garfinkel/97/22/index2a.html. Isenberg, D., "LEC of the Future Has Arrived," America's Network, Dec. 1, 1999, reprinting Isenberg's Smart Letter No. 31. Scherr, E., "Fact Sheet: Telecommunications Act of 1996," U.S. Information Agency, 1996. The Bells were major users of Telcordia's OSS, known as TIRKS (originally Trunk Inte- grated Record Keeping System but widely expanded in capability since its name was given), which was rumored to be one of the largest computer applications in production in the world, with more than 15 million lines of code. The originating leg of a switched access call, when a local subscriber i