Merge less important categories into a broader group
For multi-category part-whole charts, use category grouping on smaller or less important parts to improve readability and mitigate reader overwhelm from too many visible categories.
- purpose:refine
- basis:heuristic
- lever:encoding
- operator:part-whole
- data:categorical
- group-cardinality:many
- quality:readability:use
- polish:declutter
advice
Group the smallest categories together
Combine the least important categories into one broader group when the chart shows too many parts. For example, turn several small slices into an “Other” segment or replace multiple related categories with a larger regional or topical group in a pie, stacked bar, or area chart.
reason
Reduce overload by reducing visible parts
A chart with too many visible categories can overwhelm readers before they begin to interpret it. Grouping the smaller or less important categories lowers the number of items readers must track and makes direct labeling easier.
Mechanism: Fewer visible categories reduce clutter, simplify labeling, and keep the reader’s attention on the categories that matter most.
Evidence: The post recommends grouping unimportant categories together into one, including “Other” sections or bigger umbrella categories, and notes that this can make direct labels easier to place and reduce reader overwhelm (Muth, 2022).
context
Use when many small parts crowd the chart
- User Goal: Make a part-whole chart easier to read.
- Task: Show the main categories without overwhelming the reader.
- Data: Many categorical parts are present, including small ones.
- Chart Setting: A pie chart, stacked bar chart, or area chart with limited labeling room.
- Audience: Readers scanning for the main categories.
- Success Criterion: The chart shows fewer, clearer parts and labels fit more easily.
exceptions
Do not use when small categories must remain separate
Break it when: The individual small categories still need to be shown and named separately. Why: Grouping removes their separate identities.
costs
Accept a loss of detail
Sacrifice: You give up individual detail for the grouped categories. Risk: Readers cannot inspect the grouped small categories one by one in the main chart. Mitigation: Reserve grouping for categories that are genuinely less important to the message.
mistakes
Avoid preserving every tiny category
Mistake: Keeping all small categories separate even when they crowd the chart and do not matter equally. Why it fails: The chart becomes harder to scan and label without improving the main takeaway.
check
Test whether grouping reduces overload
Failure Sign: The chart feels overwhelming because it shows too many small categories. Quick Check: See whether an “Other” group or larger umbrella category would free enough space for clearer labels. Stronger Test: Compare the current chart with a grouped version and keep the grouped version if readers can grasp the main categories more easily.
fix
Merge the low-priority parts
- Group the smallest or least important categories into an “Other” segment.
- Replace several related small categories with a larger umbrella category when that grouping is meaningful.
- Directly label the grouped category so readers know what has been combined.