Goodhart's Law

ELI5 — The Vibe Check

Goodhart's Law: 'When a measure becomes a target, it ceases to be a good measure.' Measure lines of code? People write verbose code. Measure ticket velocity? People split tickets into micro-tasks. Measure test coverage? People write useless tests. The metric gets optimized, but the goal doesn't.

Real Talk

Goodhart's Law warns that optimizing for a metric rather than the underlying goal corrupts the metric's usefulness. In software: targeting lines of code incentivizes verbosity, targeting velocity encourages story point inflation, targeting coverage produces assertion-free tests. Effective measurement requires multiple complementary metrics.

When You'll Hear This

"Goodhart's Law is why our 95% coverage target produced hundreds of tests that assert nothing." / "We track DORA metrics as indicators, not targets — Goodhart's Law applies."