What it is
A stacked column chart places the values of several series on top of each other. The full height of each column is the total; each coloured segment is one part of it.
It answers two questions at once — how big is each total, and what is it made of? — at the cost of making the middle segments harder to compare, because they no longer share a baseline.
✓ Use it when
- The parts genuinely add up to a meaningful total: sales by product per quarter, energy by source per year.
- The totals matter as much as the parts.
- There are only a few parts — two to five segments stay readable.
✗ Avoid it when
- You need to compare one part across categories precisely — only the bottom segment has a common baseline. Use grouped columns.
- The parts don’t add up to anything meaningful (temperature and rainfall, say).
- The values include negatives — stacks of mixed signs are very hard to read.
Tips for a better chart
- Put the most important or most stable part at the bottom, where it has the baseline to itself.
- Keep the segment order and colours the same in every column.
- If the totals differ hugely and you care about the mix, switch to a 100% stacked chart.
The maths
For category i with parts vi1 … vik, segment j spans from the running sum Si,j−1 = Σm<j vim to Sij. The column’s height is the total Sik.
Only the first segment and the total start from a fixed line. Every other segment is judged by its length alone, without a common scale — the reason middle segments are compared less accurately (Cleveland & McGill 1984).
A little history
Divided or “component” bars appear throughout the statistical atlases of the late nineteenth century, and Willard Brinton’s Graphic Methods for Presenting Facts, the first popular book on business charts, gave them a chapter of their own (Brinton 1914). They became a staple of the consulting slide, where a stacked column shows a market and its segments in one picture (Zelazny 1985).
Questions
Stacked or grouped columns?
Stacked when the total matters and the parts add up to it; grouped when you need to compare the same part across categories precisely.
How many segments can a stack have?
Up to about five stay readable. Fold the smallest into “Other” beyond that.
References
- Brinton, W. C. (1914). Graphic Methods for Presenting Facts. New York: The Engineering Magazine Company.
- Cleveland, W. S. & McGill, R. (1984). Graphical perception: theory, experimentation, and application to the development of graphical methods. Journal of the American Statistical Association 79(387), 531–554.
- Zelazny, G. (1985). Say It with Charts: The Executive’s Guide to Successful Presentations. Homewood, IL: Dow Jones-Irwin.