Pareto Analysis

Origin. Pareto's income distribution (1896); named as a quality principle by Juran.

Mechanism. Where causes are heavy-tailed, a small subset accounts for most of the effect, so effort ranked by contribution has sharply decreasing returns. The 80/20 figure is a rough empirical regularity, not a law.

Procedure. Categorize occurrences. Count by category. Sort descending. Plot cumulative contribution. Attack until the curve flattens.

Applies to. Defect reduction, cost reduction, support-ticket triage.

Limitations. Counts frequency, not cost. The rare Limitations that ends the business sits at the tail's far end, and Pareto explicitly deprioritizes it. Never apply to safety.