What factors should influence the design of a complex system? And what is the impact of choices on both product and organizational performance? These issues are of particular importance in the field of software given how software is developed: Rarely do software projects start from scratch. The authors analyzed the evolution of a commercial software product from first release to its current design, looking specifically at 6 major versions released at varying periods over a 15-year period. These results have important implications for managers, highlighting the impact of design decisions made today on both the evolution and the maintainability of a design in subsequent years. Key concepts include:

* Data show strong support for the existence of a relationship between component modularity and design evolution.
* Tightly coupled components have a higher probability of survival as a design evolves compared with loosely coupled components.
* Tightly coupled components are also harder to augment, in that the mix of new components added in each version is significantly more modular than the legacy design.