Measure Copilot Cost per Retained Change, Not Accepted Suggestion
The article challenges the common practice of measuring GitHub Copilot's effectiveness by the number of accepted suggestions. It argues that this metric can be inflated by trivial completions that are later removed or reverted. The author proposes a new metric: 'cost per retained change.' This measures the cost of Copilot against code suggestions that remain in the codebase after a defined period, such as one week or one month. By focusing on retained changes, teams can better assess the actual productivity improvement and code quality impact of the tool. The article suggests that this approach provides a more accurate return on investment calculation for AI coding assistants. It emphasizes that not all accepted suggestions are valuable; some may introduce errors or be quickly overwritten. Therefore, tracking retention helps filter out noise and highlights the suggestions that genuinely contribute to the codebase. The author recommends that organizations adopt this metric to make more informed decisions about Copilot licensing and usage. The article does not provide specific data or case studies but presents the concept as a practical improvement over existing evaluation methods.
Developers can more accurately assess Copilot's ROI by tracking retained changes instead of accepted suggestions.