“Words should be weighed, not counted.” — A Yiddish Saying
Static code analysis tools count dependencies, calculate ratios, and assign neat scores. Yet in my experience, chasing those metrics never really made the design more modular. It’s so easy to game the scores without any improvement to the design itself. Let’s see why, and what you can do instead.
The Counting Approach
Most static analysis tools evaluate coupling by counting dependencies. Afferent coupling (Ca) counts how many components depend on yours. Efferent coupling (Ce) counts how many components yours depends on. A popular instability metric combines them into a neat formula:
I = Ce / (Ce + Ca)
The higher the ratio of outgoing to total dependencies, the more “unstable” a component is considered. Simple. Automatable. And deeply misleading.
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