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«Pie» and Its Problems: Why Pie Charts Are Disliked

A pie chart is the most commonly used diagram in presentation decks. On the surface, pie charts look simple and straightforward. Besides they have a very familiar circular shape resembling the earth, the sun and the moon. It can also be added that pizza and doughnuts have circular shape, and people’s faces are oval. Finally, the human eye is also circular in its shape.

However, when it comes to data presentation, it’s not that simple.

What are pie charts used for?

These charts show a percentage of the total, with all segments adding up to 100%. A single slice shows a portion of the whole.

There are general good practice rules in terms of the color design of your chart: from dark to light.

A doughnut chart is one of the varieties of pie charts. See the example from a McKinsey study.

When problems arise

Pie charts and doughnut charts have the same problems, namely that we can’t accurately define the area or the angle.

Too many small slices

When there is one large slice and many smaller slices, the values of which are not visually very different, it becomes difficult or almost impossible to count them.

Население США по штатам

When the choice of diagram is wrong

Fox asked which of the candidates viewers liked to watch on the screens the most, and it was possible to answer several times. And although the categories were mutually exclusive, it turned out to be a complete mess. The diagram turned out to be totally unusable.

When comparing several identical categories over time, it is better to go with a standard bar chart. In this example, the sizes of the circles, both external and internal, are not comparable and only confuse users.

However, if the categories are minimal and the values change significantly over time, visualization may be appropriate. As in this example:

When the pie is represented in 3D

Volumetric data is more difficult to read. Moreover, excessive design does not play any role.

When the legend gets in the way

Here, I show the trajectories along which the graph should be read. Because the legend was removed, it is difficult to perceive the information.

How to fix the situation?

  1. Keep the number of segments to a minimum
  2. Avoid using volumetric charts
  3. Don’t use multiple pie charts to compare data
  4. Place legends within segments, not outside them

Use alternative version of the pie chart – the waffle chart.

It looks stylish and is suitable for those cases when you want to focus on a small slice.

I can’t help but share the beauty of the following charts: