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Data & Analytics · Foundational

Truncated Axis

A y-axis that does not start at zero, exaggerating differences; misleading for bar charts but sometimes acceptable for line charts if clearly labeled.

Definition

Because bar length encodes value, bar charts must use a zero baseline. Line charts emphasize change, so a non-zero baseline can be appropriate when disclosed.

Exam tip

Bars need zero baselines; lines can use a non-zero baseline if it is clearly marked.

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