It’s Pie Time We Addressed Pie Charts

Pi Day, the quirky math holiday, nay, the cultural phenomenon arrives once a year on March 14. Mathematicians celebrate the beautiful oddity of a number with a seemingly infinite number of numbers. The general public eats pie. And marketers have their own pie to consider: Pie charts.

However, while mathematicians agree on the beauty of pi, and the general public agrees on the deliciousness of pie, marketers and data visualizers do not agree on the effectiveness of pie charts.

What makes this humble, out-of-the-box data visualization that we all learned about in elementary school such a divisive chart? Regardless of how you recently celebrated Pi Day, in this post we’ll honor the holiday by exploring the benefits and shortfalls of pie charts, using the most appropriate set of data to illustrate examples: favorite pie flavors.

Benefits and Shortfalls of Pie Charts

Despite the ease of creating a pie chart, they’re often not very effective at communicating data. As a rule of thumb, when you design a pie chart, keep this in mind: how easy is it to understand what the top three results are?

Benefits

Two benefits of pie charts are that they are relatively universal and that people understand the concept. You don’t need to explain to your audience how the chart should be read. They also understand that the chart should communicate that all pieces of the whole should add up to 100%.

Others claim that they are useful for comparing angles rather than area, and that when faced with a side-by-side comparison about expectation versus the result, it’s easy to see when a pie chart slice is greater than 25% or 50%.

Shortfalls

Several elements make this out-of-the-box pie chart difficult to comprehend.

This example of a pie chart is made up of 12 different sections, each representing a different favorite flavor of pie, and each slice identified with a different color. This example of a pie chart is made up of 12 different sections, each representing a different favorite flavor of pie, and each slice identified with a different color.
It’s difficult at a glance to understand which slices of the pie are the biggest.

 

For one thing, it isn’t very easy for people to distinguish between the slices of the pie chart if they are similar in size. Take the two biggest pieces of the pie – Pecan and Pumpkin. Which slice is bigger? Or comparing Dutch Apple and Key Lime, which holds the rank of third-favorite pie flavor?

This brings us to the second element: color. What do these colors mean? Are they representative of anything? Aside from missing the mark on web accessibility for colorblind users, it’s unclear what, if anything, these colors should represent.

The lack of clarity of colors and size of slice speaks to the need for labels. The slices, as well as the portion of the pie they represent, should be clearly marked. Despite the added labels, you’ll notice this chart still takes some comprehension and time to identify the top three pie flavors.

Even with lines drawn connecting each flavor of pie and it's % value, it still provides a lot of information to sift through.Even with lines drawn connecting each flavor of pie and it's % value, it still provides a lot of information to sift through.
Labels can help clarify the percentage of each slice, and indicate what each piece represents. But it’s still a lot of information to process.

Additionally, the slices of the pie should equal 100%. If you’re working with data where there is overlap and the total value is greater than 100%, a pie chart is likely not a good fit.

Finally, a pie chart can be further distorted with 2D versus 3D formatting options. The 3D option might look fancy, but it distorts the visual so that the bigger slices may look smaller, and vice versa. Stick to 2D pie charts to maximize comprehension of these charts.

In this example, creating a 3D version of the chart doesn't help the visual clutter, and in fact falsely makes some section appear to be larger than they actually are.In this example, creating a 3D version of the chart doesn't help the visual clutter, and in fact falsely makes some section appear to be larger than they actually are.
3D visuals can sometimes distort the sizes of the pie slices.

What to Use Instead of a Pie Chart

If you’re struggling to make a pie chart that is an effective representation of the information you’re trying to convey, consider this alternative to visualize data that might get your point across in a more efficient way: a sideways bar graph.

This is a common alternative to pie charts. It is a quick visual that shows the top three pie flavors at a glance, and the actual values of data, rather than being a portion of 100%.

In this example, the same information that was confusing when displayed as a pie chart is much easier to read as a sideways bar graph. The first four lines show that pumpkin and pecan are the first and second favorite flavors, while key lime and dutch apple are tied for third.In this example, the same information that was confusing when displayed as a pie chart is much easier to read as a sideways bar graph. The first four lines show that pumpkin and pecan are the first and second favorite flavors, while key lime and dutch apple are tied for third.
A sideways bar graph is a great alternative to pie charts, when you’ve got a larger set of variables with similar values.

Here, we see that Pumpkin is the frontrunner, Pecan is a close second, and that Key Lime and Dutch Apple are actually tied for third place.

If You Must Use Pie Charts

If you’re a pie chart aficionado and insist on using them, here are some tips to make them more comprehensible.

Use Labels

As we saw earlier, the addition of labels provides clarity of which values are ascribed to each slice. This takes the guesswork out of wondering about the sizes of slices.

Put The Slices in Ascending Order

Putting the pie chart in ascending/descending order removes another element of guesswork – Understanding the order of pie slices. Here, we can quickly tell that Pumpkin is the most popular pie flavor, Pecan is the second favorite pie flavor, and Dutch Apple and Key Lime are the third favorite pie flavors.

By rearranging the pie chart, the three largest sections all occur on the left, making it straightforward what the top flavors are.By rearranging the pie chart, the three largest sections all occur on the left, making it straightforward what the top flavors are.
By reorganizing the slices of the pie in ascending order, it’s much easier to see the top three values in this data set.

Remove Unnecessary Colors

The pre-prescribed colors of this pie chart add another level of potential confusion. Do the colors mean anything? Are all “fruit” pies intended to be one hue, and “chocolate/other” pies meant to be another?

If colors aren’t adding meaning to your chart, simplify it by removing them, or using an abbreviated color palette to highlight the meaningful parts. This helps support the original goal of understanding the top three pie flavors.

The same pie chart has been given a much simpler color scheme. The top three pie flavors are represented in different shades of blue, with the rest of the slices showing in gray. This immediately draws a reader's eyes to the pertinent information in this data set.The same pie chart has been given a much simpler color scheme. The top three pie flavors are represented in different shades of blue, with the rest of the slices showing in gray. This immediately draws a reader's eyes to the pertinent information in this data set.
By using a limited color scheme, attention is more easily drawn to the data that you want your audience to focus on.

 

In Other Words

Pie charts are not something to avoid altogether; however, they should be used with appropriate data. And when creating pie charts, formatting should be considered to make them easier to read, no matter how you slice it. So yes, you can have your pie chart, and use it in reporting, too.

The post It’s Pie Time We Addressed Pie Charts appeared first on Portent.


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