Figure 2. (Top) Network Modernization Index, 1988 to 1993. (Bottom) Cumulative Shareholder Index, 1988 to 1994. NOTE: Substitution rates measure how rapidly new network technologies replace old ones. Network Modernization Index is the average of substitution rates for the following technologies: Digital-SPC Access Lines, SS7-317 Access Lines, ISDN Access-Line Capacity, Fiber and Digital Links, and Fiber-Equipment Channels. SOURCE: FCC ARMIS Reports, Compustat, and One Source.