21 / UX Laws

Pareto Principle

A relatively small set of causes often accounts for a large share of the outcome.

Visual proof

Look for concentrated impact, but do not assume the ratio before you measure it.

Story

A support team groups a quarter's tickets and finds that three recurring problems create most of the volume. Fixing those flows can remove more friction than polishing dozens of isolated edge cases.

Origin

Joseph Juran applied the idea of a vital few to quality management and attached Pareto's name to it. He later acknowledged that the attribution was imprecise. The familiar 80/20 split is a heuristic, not a constant.

Field Rules

  • 01

    Measure the distribution before prioritizing. Usage, error, support, and revenue data may reveal concentration, but the split may not be 80/20.

  • 02

    Invest deeply in high-impact tasks. Make the frequent path clear, reliable, fast, and accessible before polishing rarely used variations.

  • 03

    Do not confuse low frequency with low importance. A rare safety, payroll, or recovery task can still deserve first-class treatment.

  • 04

    Revisit the analysis as the product changes. The vital few can shift when users, workflows, or business conditions change.

Examples

Digital systems

Support themes that drive the backlog

Tickets are grouped by underlying cause rather than handled as isolated complaints. The team fixes the few flows responsible for most repeated contacts.

Physical signals

Maintenance by failure pattern

A facilities team logs repeated faults and finds that a few components cause most callouts. Replacing those components reduces more disruption than treating every fault equally.

Application

Everything receives equal priority

Time is spread across many issues without checking which ones create most of the cost, friction, or risk.

Resolves with
Find the concentration of impact

Group outcomes by cause, rank them with evidence, and focus on the few improvements that change the result most while protecting critical exceptions.

Sources