State the value in text instead of drawing a two-slice pie chart
For binary part-whole communication on a single total, use text instead of a pie chart to improve readability and mitigate charting a second value that is only the remainder to 100% for readers.
- purpose:select
- basis:heuristic
- chart:text:use
- chart:pie-donut:avoid
- lever:chart-family
- operator:part-whole
- group-cardinality:binary
- quality:readability
advice
Use text for a two-value whole
State the one percentage directly in text when the data has only two values that sum to 100%. For example, replace a two-slice pie chart with a sentence that names the main share instead of charting that share and its remainder.
reason
Why a two-slice pie often adds little
When a whole is split into only two values, the chart effectively repeats one number and its complement. Stating that number directly can say the same thing without adding a chart.
Mechanism: The text presents the only independent value directly, rather than drawing both the value and 100% minus that value.
Evidence: The source says pie charts might be unnecessary if you only want to show two values, because that is effectively one value and the difference between it and 100%, and suggests mentioning the one number in the article instead of showing a chart (Muth, 2018).
context
Use when the data is only one share and its remainder
- User Goal: Communicate one share of a whole.
- Data: Two values that sum to 100%.
- Chart Setting: Deciding whether a pie chart is needed at all.
- Success Criterion: The key percentage is clear without extra charting.
exceptions
Do not use when the whole has more than two shares
Break it when: The data contains more than two values. Why: The display is no longer effectively just one independent number and its remainder.
costs
Tradeoffs of choosing text instead of a chart
Sacrifice: You stop showing the complementary share as a separate slice. Risk: Readers must infer that the second share is whatever remains to 100%. Mitigation: State the one percentage directly in the surrounding text.
mistakes
Common misuse of the two-slice pie
Mistake: Drawing a pie chart for one value and its remainder. Why it fails: The chart uses a full display for information that is effectively one number.
check
Check whether the chart is unnecessary
Failure Sign: The pie chart has only two slices. Quick Check: Remove the chart and see whether the message still works as one stated percentage in text. Stronger Test: If the article sentence already communicates the key share clearly, keep the text and drop the pie chart.
fix
Fix the chart choice for a two-value whole
- Count the slices before publishing the pie chart.
- Remove the pie chart when it only shows one share and its remainder.
- State the key percentage directly in the article text.