Why 'code survival' may be the only engineering metric that resists gaming

A software engineering analysis argues that most developer productivity metrics — including lines of code, commit counts, velocity, and DORA scores — are easily gamed because they measure activity rather than genuine output. The piece applies Goodhart's Law, noting that once a metric becomes a target, engineers naturally optimize for the number rather than the underlying work it was meant to reflect. The author proposes 'code survival' — tracking whether specific lines of code remain intact at the latest codebase version over time — as a structurally harder metric to manipulate. A time-decayed git blame approach is described, where a line's score fades unless it persists and gains additional weight when other developers build upon it, a quality termed 'gravity'. However, the analysis also acknowledges a residual loophole: repeatedly touching one's own code resets its age weighting, meaning raw survival scores can inadvertently penalize stable, untouched code while rewarding frequently revised work.