How Google’s Code Review Frequency Changes With Engineer Experience
A brief analysis of Google’s code review data shows an average of five comments per 100 lines of code and two comments per change, with comment density decreasing from eight per 100 lines for new hires to 4.5 after three years of experience.
According to a recent case study titled “Modern Code Review: A Case Study at Google”, the average number of review comments is about five per 100 lines of code, and each code change receives roughly two comments.
The data also shows a clear trend: as engineers gain more experience at Google, the density of comments per 100 lines declines. New hires receive about eight comments per 100 lines. After one year the rate drops to 5.5, after two years to five, and after three years to 4.5 comments per 100 lines.
The image below visualizes the Google code‑review rate.
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