Alberto Cairo, Knight Chair in Visual Journalism at the School of Communication of the University of Miami, gave a wonderful EUNIS 2020 keynote on Making Good Visualisation Decisions. His argument – Visualisation is like writing: there are basic (grammatical) rules, but also choices, and those should be reasoned. Bad decisions can cause real-world harm. Just three of my highlights from his presentation.
How, even whether, to use visualisation must be appropriate for the context. A cartoon bubble map of Google searches beginning “Why does my dog/cat…?” is great for the cover of a report. A representation of COVID-19 statistics by anyone who does not understand epidemics is very different.
The choice of visualisation style must be led by the message you want to convey, not by incidental features of the data. Just because numbers sum to 100% doesn’t mean they should be displayed as a pie chart; just because a table contains geographic data doesn’t mean they should be shown as a map. Don’t be afraid to explain your visualisation and to highlight key points. This will make it accessible to many people who find visual presentation hard to read and may help increase visual literacy. The Financial Times has an excellent visualisation vocabulary.
And use visualisation yourself to identify, understand and, if necessary, correct outliers. On any statistics of internet use, the state of Kansas is likely to be one of these. Not because of anything to do with the population, but because it’s the geometric centre of the country, and that’s where many geo-location tools show VPN accesses as coming from!