A story told with data: the conclusion headline and one accent

Data storytelling joins numbers, a conclusion and a way of showing them: the title states the point, one accent marks the key, text describes it.

Numbers don’t speak for themselves

Every project has numbers: times, prices, how much was done. It is easy to put them in a table, and they will lie there until the reader works out what they mean. Data storytelling is three things together: the data itself, the conclusion (what it is about) and the presentation (how it is shown). Books on it give different formulas, and the best known is Cole Nussbaumer Knaflic’s storytelling with data (2015), but the point is the same: a chart should hold an idea, and the reader shouldn’t have to hunt for it.

Look at the diagram: the same five numbers are shown in three ways.

Step 1: one idea

Start with a question: “What should a person take away from this picture?” The answer should be one sentence. If there are two, they are two charts.

A good chart title is a conclusion, not a caption for the axes.

• Weak: “Time to settle a matter, by quarter”.
• Stronger: “Settling a matter now takes two weeks, down from half a year”.

A reader who has read the title already knows the answer. The chart is there so they can be sure.

Step 2: a fitting shape

Not every number needs drawing. A short rule for a site.

• Two numbers. Write them large in the text: “it was 6 months, now it’s 2 weeks”. A chart is excess.
• Comparing several quantities. Bars: readers compare their lengths fastest.
• Change over time. A line, or bars by year.
• Exact values. A table.

Pie charts with many slices read worse than bars: comparing angles is harder than comparing lengths.

Step 3: remove the clutter, highlight one thing

A good chart is like a good photograph: there is little in it that isn’t needed. What can go: frames, a grid, depth (“3D”), a legend if the labels can sit right at the bars. What stays: the numbers and the names.

Then highlight one thing: with color, a frame or an arrow. The highlighted part draws the eye, and the gray rest serves as background. If three bars are highlighted, you have highlighted everything, which means nothing.

Step 4: honesty

A chart persuades faster than text, and that is easy to abuse. A few rules.

• The scale of bars starts at zero. If you “cut off” the start of the scale, a three percent difference looks like a cliff. That is how misleading charts are made.
• Compare the same thing. Measure “time before” and “time after” in the same way.
• Show the source and the date. “Our figures, 2025, 40 requests”.
• Don’t pick convenient points. If you show the best month and say nothing of the others, the reader works it out later.
• Small samples. Don’t write “on average” over ten cases. Write “in ten cases”.

In the US, the FTC treats a chart in an advertisement like any other claim: it must not mislead, and you need evidence for what it implies. In the UK, the CAP Code asks the same of numbers and charts in marketing. This is general information, not legal advice.

Step 5: access

Some readers won’t see the chart: a person with low vision, a screen reader user, someone whose image didn’t load. They need a text alternative: one or two sentences with the main number (“The time fell from 180 days to 14: 13 times shorter”). Detailed tables and complex charts are covered by the W3C in its guide to complex images (the link is at the end), and the Web Content Accessibility Guidelines ask for the alternative (success criterion 1.1.1). In the US the ADA is often applied to websites through these guidelines, and in the EU the European Accessibility Act points to the same standard; the quality and law part comes back to this.

Remember color, too. If a value is given by color alone (“the bad ones are in red”), a person with a color vision deficiency won’t see it (criterion 1.4.1). Add a label or another shape. Labels must have enough contrast.

In the practice you will build the chart not as a picture but with ordinary page elements: bars and labels. Every program can see it, it reads without loading anything, and it can be checked.

Practice

Build a bar chart about your project.

1. Numbers. Take the times, prices or counts of your services or products. Don’t invent exact figures if you don’t know them: for a practice page, estimates are fine, but say so in the source.
2. Rows. Label each bar with the name of your service from the brief and write its value. Set the length as a percentage of the largest.
3. Title. A conclusion with a number or a comparison.
4. Accent. One. The class accent on one bar.
5. Source and date.
6. Alternative. One or two sentences with the main number.

If numbers don’t suit your project, take imaginary ones, but mark them in the source, as is done in the diagram above.