In 1990 a project was established at AT&T to build applications that manage telephone systems. Since then the project has successfully completed over 20 applications comprising about 500,000 lines of source code. These systems are used daily by hundreds of managers and operators to monitor and provision the AT&T long distance telephone network. The project's success can be attributed directly to an early commitment in making software reuse a major component of its software development process. A critical factor was the establishment of a feedback loop between consumers and producers of reusable software to foster continual improvement and extension of reusable code repositories. Progresses in the feedback loop are measured by five different reuse measures. While no one measure is "best'' as each provides a different perspective on reuse, two derived from the consumer/producer model have proven particularly useful: use of reusable library components and reuse growth factor. The latter, developed in this study and described below, helped uncover a new opportunity for reuse that was not obvious from other measures.