Chocolate Pie Chart

Regular readers of this blog will be familiar with my arguments against pie charts. However, I have finally found a legitimate use for pie charts - homemade chocolate! A company called Chocolate Editions has been reviewed in Wallpaper magazine for creating a chocolate pie chart. The result is 70% dark, 20% milk and 10% white chocolate. The percentages are reflected in the shape of the pie chart.

Pie charts can make you laugh

One of my favourite bloggers is Jessica Hagy. Each day she publishes an index card with a comical graph. Most pie charts are terrible but this one about "I'm fine." amused me.

Getting creative with Pie Charts

The Australian Securities Exchange (ASX) is a very successful organisation with an operating revenue of over $538 Million. However their success does not stop them creating strange pie charts. The following diagram is from page 35 of the ASX 2009 annual report.

The pie chart represents the number of referrals from the ASX to the Australian corporate regulator for possible breaches to trading laws or rules. The interesting innovation is the 'Total Referrals 88' which is the outer circle of the pie chart. Initially I thought this must represent the sum of the slices of the pie but the slices add up to more than 88. Then I spotted the asterisk indicating a single referral may contain more than one breach.

This pie chart should win an award for visual confusion. The total referrals number visually looks like it should equal the sum of the slices but it actually represents a very different number.

Pie charts are evil

I recently spoke at Ignite Sydney on the topic 'Pie charts are evil'.

Too many slices

If you have to use a pie chart - really there are better charts to explain data - then limit the number of segments on the pie chart to give the reader a fighting chance of understanding it.

The pie chart below is from Rio Tinto's 2008 annual report (Rio Tinto is one of the world's largest mining companies). Apart from being a doughnut pie chart, which makes cognition even harder, Rio has 10 segments they are trying to compare. Nancy Duarte in slide:ology recommends a limit of 8 segments in a pie chart. I think even 8 segments is too many and would go for a maximum of six segments.

Pretty pictures vs clear data representations

Graphic designers love to use colour and innovative diagrams to catch the readers eye. Unfortunately this can make it difficult to analyse any underlying data.

Below is a pie chart taken from the 2008 annual report for Westfield (the worlds largest shopping centre owner). Pie charts are difficult to analyse because the reader is expected to compare the differences in the angles of the pie slices. This pie chart also has a strange choice of colours with New Zealand and United Kingdom having very similar colours making it difficult to differentiate between them. The faint shadowy circle within the pie is also distracting.