You might expect that the chart is ordered from highest to lowest amount, but more careful examination proves that hypothesis incorrect. It’s actually ordered by distribution amount – creating the false impression that as returns decrease so do their slice of donut.
- When creating a visualisation, always start off with the question you are trying to answer. When the visualisation is completed, check that it actually answer that question – clearly.
- Humans find it easier to judge length rather than area – distributions are often best displayed using histograms or bar charts, for continuous and categorical data respectively. There are other options, and rules are made to be broken – but you need to know the rules!
- Avoid introducing non-natural ordering as it can confuse your viewers.
- Pie and donut charts only make sense if you are displaying parts of a whole: in this case, we didn’t know what the whole figure was.
Cliff Taylor is an eminent journalist, well-respected in his field, and we are sure that the figures here have been correctly interpreted by him and his team – it’s just that using these visualisations, we can’t actually verify it.
In fairness, it can be hard to produce visualisations to journalistic standards and to journalistic deadlines if you haven’t been taught how to do so. The same can be true of any business reporting role, that’s why we designed our two-day “Effective Data Visualisation” course, running in September. We can show you well-established best practice, and introduce you to some excellent free software to allow you to develop intuitive, precise, meaningful visualisations, good enough for the Irish Times. You might like to come too.