This entry is part of the Chart Index, the reference library for the Chart Design Field Guide.
An area bump chart shows how both rank and magnitude change over time. Each category is a flowing band: its vertical position communicates rank, while its thickness communicates value. This makes it useful when a bump chart answers only half the question because the size of the difference also matters.
What it is
Area bump charts combine the ordered paths of a bump chart with the variable thickness of a stacked area chart. The bands are rearranged at each time point according to rank, so crossings show changes in order and thickness shows the underlying measure.
When to use it
- Rank changes over time matter, but equal-width bump lines would hide large differences in value.
- A small number of categories compete for share, volume, or attention.
- The reader needs to see both who moved and whether the movement was commercially meaningful.
When not to use it
- Precise values are the primary task. Use a line or grouped bar chart.
- There are many categories or frequent rank changes; crossings quickly become difficult to trace.
- Values can be negative. Band thickness has no natural representation for a negative quantity.
Design principles
Limit the number of bands
Five to eight series is usually enough. Beyond that, crossings and narrow bands compete for attention.
Label bands directly
Place category names at the start or end of each band. A detached legend turns tracing into a memory task.
Keep colour stable
A category must retain the same colour as it changes rank. Colour identifies the path; position reports its rank.
Explain thickness
State the unit represented by band thickness. Without that cue, readers may treat the chart as a decorative bump chart.
Anatomy
The x-axis is ordered time, the vertical order is rank, band thickness is the quantitative value, and crossings mark changes in rank.
Related types
- Bump chart - rank change without magnitude.
- Streamgraph and stacked area - composition over time without rank ordering.
- Line chart - precise change in values over time.
Reading list
- Nivo AreaBump documentation - interactive component reference and configuration.
- Cleveland, W. S. (1985). The Elements of Graphing Data. Foundations for reading position and change.