PIES ARE FOR EATING NOT FOR DISPLAYING DATA.

Recently, I have had an interesting discussion about the pie charts. My interlocutor claimed that the pie charts should be in usage because they are intuitive, and people decoding information from them very quickly. Well, it’s exactly opposite, how research shows. The human brain cannot quickly and accurately compare several angles. What is more, on the pie chart there are not only angles but areas and colours which confuse the human brain as well. As proof, check out the paper of W. Cleveland & R. McGill about the visual decoding of quantitative information. So, how to cope with part-to-whole cases? What instead of the pie charts? How to effectively convey information?

Paulina, what is wrong with you? Why do you hate those pie charts so much? Look. They are based on the ideal shape, and you can use all your most favour colours at once!

Unfortunately, those colours and this ideal shape are a true curse in the clear interpretation of the data. Research shows that the human brain has problems with decoding quantitive information presented by those three attributes:

1. angles,

2. areas,

3. colours.

Let’s see an example. Imagine that parts of the wheel are product categories which you offer in your store. You would like to find out which category is the most profitable one. What kind of question would you ask?

Which category sales the best? Which one is the worst?

Let’s see how visual decisions can affect the process and speed of getting valuable insights.

Note: I’m not adding data labels on purpose. I want to focus only on visual decoding (without text support).

PIE CHART

I would never choose a pie chart to compare more than two categories. Are you able quickly and accurately answer questions statement in the example? I’m not. NOT AT ALL.

100 % STACKED BAR CHART

We can instead of pie chart use 100% stacked bar chart, up to some point. Research shows that people are quite good at comparing lengths. However, colours can distort lengths. The more saturated colours, the larger the object seems to be. The second issue is again with many categories. The more of them, the workload for comparing elements increase.

STACKED BAR CHART

This is my first choice. There is no field to mislead anybody with a stacked bar chart.

As I mentioned, people are quite good at comparing lengths. When we use one colour of bars, we can be 100% sure that no one will have issues to recognize the longest and the shortest bar. One blink of an eye and you understand what you see. For your lazy brain, it is pure magic.

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