One message per chart
A chart showing six series over three dimensions communicates nothing. Decide what the reader should conclude, then show only what supports that conclusion.
If you cannot write the chart's message as a single sentence, the chart is not ready. That sentence should usually be the title.
Always compare against something
- The same period last year, for seasonal businesses
- The target, if there is one
- The previous period, where seasonality is not a factor
- Other categories, for composition questions
A number alone is not information. A number against a comparison is.
Remove everything that is not the data
- No decoration, gradients or three-dimensional effects
- No legend where direct labelling would do
- Gridlines faint or absent
- Axes starting at zero for bar charts, always
- Colour used to distinguish, not to decorate
Choose the right chart
| Question | Chart |
|---|---|
| How has this changed over time? | Line |
| How do these categories compare? | Bar |
| What is the composition? | Stacked bar, rarely pie |
| Is there a relationship? | Scatter |
| What is the distribution? | Histogram |
| A single important number | Just the number, large |
That last one is underused. Sometimes the right visualisation is a number in large type with a comparison beside it.
Write the conclusion
Every chart in a business report should carry a sentence saying what it shows and what it implies. Readers should not have to work it out.
That sentence is also the test of whether the chart was worth including at all.