Crime taxonomy · Drawing and geometry

Inappropriate chart type or encoding

A chart type that hides the comparison it is supposed to show.

What it looks like

The chart form fights the data: a pie with a dozen slices, a line connecting unordered categories, a stacked chart where the interesting series floats on a wobbly base.

Example

The same data shown honestly: A sorted bar chart makes the ranking and every value readable at a glance. — **The fix.** A sorted bar chart makes the ranking and every value readable at a glance.

Why it is bad

People are poor at comparing angles and areas, so many-slice pies make rankings unreadable.
A line between categories implies a sequence or trend that does not exist.
It is usually careless rather than malicious, but readers still walk away with the wrong idea.

How to fix it

Use sorted bars for comparing categories, lines for change over time, scatter plots for relationships.
Keep pies to two to four slices, if at all.
Group small categories into "Other" and show it last.

When it is not a crime. A two-slice pie (yes/no, share of a total) is perfectly readable.