---
{
  "schemaVersion": 1,
  "id": "DR-002",
  "title": "Rule of Proportion",
  "summary": "Visual magnitude reflects numerical magnitude.",
  "enforcement": "automated",
  "htmlUrl": "https://lanej.io/viewrule/rules/dr-002/",
  "markdownUrl": "https://lanej.io/viewrule/rules/dr-002/index.md",
  "source": "docs/design-rules/DR-002-proportional-magnitude.md",
  "sourceSHA256": "28943b98ebc6360cfcd0c1ac754b5b60322c7559e9c2897a546569d69d1bfd0b"
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---

# DR-002 — Rule of Proportion

**Principle:** Visual magnitude reflects numerical magnitude.

**Requirement:** Ordinary bars representing amounts must start at zero. Filled
area charts representing amounts must preserve a zero baseline. Bubble area
must be proportional to its encoded value. Decorative 3D projections must not
distort a two-dimensional quantitative comparison.

**Why:** The size of the visual mark must represent the quantity faithfully.

**Exception:** Range bars and timelines represent intervals; their endpoints must
represent those intervals accurately. Unfilled line and scatter plots may use
nonzero domains to reveal variation. Actual three-dimensional data may justify
a three-dimensional view. Axis labels must make the chosen mapping clear.