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Answer: Any graphic should be proportionately correct or drawn to scale. Avoid distortions that mislead the reader.

SEC handbook

• Avoid graphics that start at a non-zero baseline; they distort differences by destroying correct proportions.
• Draw graphics to scale: a barrel isn't 50% bigger when production only went up 25%.
• When you group graphics side by side, avoid changing the scale from one to another; mixing billions, millions, then dollars can mislead the reader.
• Don't reverse time: in graphics showing information over time, time should flow forward.
• Trust your eye: if a graphic seems unclear or unhelpful to you, it probably is, whatever guidelines it follows.

U.S. Web Design System

• Line chart origins should start at zero, unless clearly noted.
• Provide a textual representation of axis values and labels, and a tabular version of the underlying data.

See also

• plain-simple-charts
• plain-explain-numbers-do-the-math

Claims

• id: C1 claim: SEC: avoid non-zero baselines. source: S1 evidence: "avoid graphics that start at a non-zero baseline"

• id: C2 claim: SEC: time should flow forward. source: S1 evidence: "time should flow forward, not backward."

• id: C3 claim: SEC: keep scales consistent across grouped graphics. source: S1 evidence: "avoid changing your scale from one graphic to another"

• id: C4 claim: USWDS: line charts start at zero. source: S2 evidence: "Line charts origin should start at zero, unless clearly noted."

Sources

• [S1] A Plain English Handbook. U.S. Securities and Exchange Commission. https://www.sec.gov/pdf/handbook.pdf . License: US government work, public domain. Accessed 2026-11-09.

• [S2] Data visualizations. U.S. Web Design System (GSA). https://designsystem.digital.gov/components/data-visualizations/ . License: US government work, public domain. Accessed 2026-11-09.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted). Sources: US federal government works (GSA, GPO, SEC, CDC), public domain in the United States; third-party quotations inside those works were not used. Text was condensed and changed from the originals.

@misc{iil_note_5bmffse1,
  author = {{iinventedlight}},
  title = {{Draw charts to scale with a zero baseline and forward time}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-09},
  url = {https://iinventedlight.com/library/notes/plain-honest-chart-scales/},
  note = {Permanent ID iil:note:5bmffse1. License: CC-BY-4.0.},
}

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