A finished chart has annotations. A draft chart has none. The difference is the difference between leaving the reader to find the point and showing them the point. The FT, the Economist, and Bloomberg pages are dense with inline labels, callout arrows, and reference lines because their editors know that annotation is half the chart.
Three annotation moves
- Inline label: put the series name at the end of the line, instead of in a legend. The eye doesn't have to jump between key and chart.
- Callout with arrow: 'Recession begins here →' pointing at a specific point. Used sparingly, this is the most powerful annotation; used everywhere, it becomes noise.
- Reference line: a dashed horizontal at the target, baseline, or industry average. Turns 'we hit 12%' into 'we beat the 10% target'.
Replace the legend
On most line charts with ≤4 series, you can place the series name at the right end of each line in the matching colour. The legend becomes unnecessary. The reader's eye doesn't have to leave the data to identify the line. This single change improves readability more than any palette choice.
When to highlight, when to ignore
Annotate the data point that the action title is about. If your title says 'enterprise revenue grew 4x', annotate the enterprise line at its peak, not the SMB line. If your title says 'European margins lag the US by 12 points', put a vertical bracket on the chart showing the 12-point gap with a label. The annotation is the title's argument, drawn.
Action title: 'Latency dropped 40% after the migration'──────────// ← Migration (Aug 2025)────────────| The 40% drop, annotated.
Source attribution is itself annotation
Every publication-grade chart has a source line: 'Source: Central Bank of Kenya, May 2025'. It's small, it's grey, it sits below the chart. Its presence signals credibility. Its absence signals 'I built this in Excel'. Source even your own analyses: 'LeadAfrik analysis based on KNBS Q1 data' is more credible than the same chart with no source line.
Over-annotation
An annotation on every data point is the same as no annotations. The reader sees a noisy chart and reads nothing. Pick the one or two points the chart's argument depends on, annotate those, leave the rest clean. Restraint is signal.
Exercise
Take a chart you've made. Identify the single data point that your action title depends on. Add an inline annotation that points to it and names what it shows. Remove the legend if you have one and put inline labels instead. How does the chart's argument read now compared to before?