Defect ratio

What it measures

The share of merged PRs classified as bug fixes each week, as a percentage.

Why it matters

Defect ratio is the quality counterweight to the speed panels. A team shipping faster while its bug-fix share climbs is borrowing against quality.

How to read it

• Read it alongside Throughput and Cycle time — speed and this number tell the story together.
• Classification checks PR labels first (an explicit toil label like chore or refactor always wins), then the labels on any issue the PR closes, then title patterns; it is a heuristic, not a bug tracker.

Anti-blame

A team-level percentage. Which PRs were fixes is never tied to who wrote them.

Common misreads

A rising defect ratio is not automatically bad — it can mean more fixing of old issues, not more new bugs. Investigate before concluding.

The closing-issue check can overshoot: a large feature PR that closes a bug report it happens to obsolete, an unlabelled umbrella PR closing several issues where only one is a bug, or an issue labelled both bug and something else, all count as a full bug fix. It only backs off when the PR itself carries an explicit toil label (chore, refactor, docs, and the like) — anything else, including a bare title, still inherits the issue's verdict. The correction only adds counted fixes, never removes one, so a sudden jump is a prompt to look at what was actually closed, not proof the team broke more.