Data Visualisation: Why Pie Charts are Dead!
Given the increasingly data driven landscape and the evolving data visualisation world that despite seeing improvements over recent years has seen relatively few significant changes. With most advances being derived from increased data availability (more data = more data to draw meaningful interpretation from), changes to data visualisation itself not so much. That will likely change soon with the advances in Augmented Reality and Spatial Computing, see the picture below of Microsoft Power BI in Apple Vision Pro!
But nevertheless, Data Visualisation primarily remains the same as it has been, aiming to facilitate easy visual representation and therefore interpretation of data. This leads us to focus on the basics of visualising data and the crux of this post, Pie charts are useless and that despite their popularity the “fun” is over.
It might be hard to accept but pie charts have had their fun, if you've been guilty of putting pie charts in every single PowerPoint deck you've created since the 90s then this might be a terrifying thing to hear... but for others, like myself they have had their moment, let it go!
I am not alone in this viewpoint, those interested in all things Data Visualisation will have heard of Stephen Few he focuses on practical uses of data visualisation and states “Of all the graphs that play major roles in the lexicon of quantitative communication, however, the pie chart is by far the least effective”. In other words, useless!
This isn't a new viewpoint either Pie Charts, whilst probably present in almost every single Data Visualisation Dashboard and Report their ineffectiveness has long been highlighted.
But Why? Why Are Pie Charts useless?
When comparing more than two categories, pie charts make it really really easy for us to misrepresent or quantify the percentages and correlation to each other.
Using an example collated by Stephen Few, if you consider the Pie Chart below its evident Company C (Green) is 25%.
But if you look at the next Pie Chart, it’s no longer as easy…
But why not just add labels?, good question. Consider the example below, are any of the pie charts intuitive. In the first Pie Chart (A), the blue, red and green slices all look similar… but when looking at the histogram they are evidently different.
Sure, adding labels would help, but doesn't that make the visual portion of the pie chart the actual visualisation itself redundant?
So why does this all matter?
Why not just use a pie chart in your Sales Pitch or Monthly reporting dashboards? Consider what the true purpose of a report or dashboard is, what the purpose of data visualisation is. The aim is simple, to provide a graphical summary of data that allows the user to interpret with ease i.e. Truthful (Inform and not influence). Pie Charts, aren't always that easy..
But hey... don't they look pretty!
