Usages and Designs for Pie Charts

Usage and Design of Pie Charts

    Pie charts are a type of data visualization that organizes data as a whole, represented as a circle or pie that is divided into slices, each slice is a category that is proportional to the value of the overall data. In terms of percentage values, each slice added together should equal 100%. The purpose of a pie chart, as Tableau states, "helps the user compare the relationship between different dimensions (Ex. categories, products, individuals, countries, etc.) within a specific context." (Tableau). However, due to the human mind's difficulty with interpreting area, volume, and curvature, it is best for visual clarity that pie charts are made up of only 3-4 slices or categories, with a maximum of 5 slices if necessary for the subject at hand. Typically, a pie chart is chosen to emphasize a specific category that stands out among the rest, crafting a narrative around the significance of that particular slice in the context of the larger data subject.

Figure 1: Pie Chart

    Using the 2024 Browser Market Share Worldwide dataset from StatCounter GlobalStats, I created a pie chart that visualizes the market share (usage) of common browsers from across the world. Arranging the chart to showcase the top 4 browser categories, such as Chrome, Safari, Microsoft Edge, and Firefox, with the other browsers, like Opera or Samsung Internet, combined together and represented as the Other category. As you can see, the difference between the areas of each slice helps to highlight the significant portion of the chart held by Chrome, indicating that in 2024, Google Chrome dominated the global market share over other browsers, such as Safari and Edge. With the second version of my pie chart, reinforce that story by shadowing the other distinctive colors of gray while keeping the Chrome slice as its bright red, as demonstrated under the Great Examples of Pie Charts section in Tableau's Pie Chart article, to quickly inform viewers which slices are significant and most important to the narrative of the visual and reiterate the area difference between the smaller and larger slices through careful color choices. 

Figure 2: Highlighting Slices

    During the design, I implemented recommendations from articles such as Pie Charts Best Practices by Anastasiya Kuznetsova, who suggested data labels with percentages be positioned outside their respective slices,  removing the legend, and matching the font with the slice's color for conformity, which I was unable to do in my version of Excel without changing all of the font colors to the same one. As well as following along with visualization and Excel guides, Effective Data Visualization 2nd Edition by Stephanie Evergreen, who advised removing the white space/outline between slices that Excel automatically applies, and since Chapter 1 - Why We Visualize, never use 3D pie charts as 3D exacerbates the visual clarity issue already present with pie charts due to slice area being hard to decipher for the human mind. 

Alternative Formats for Dataset

    However, even with a validly designed pie chart, other visualizations can be used to visualize the worldwide browser market share in 2024. One prominent example would be a bar chart that utilizes the lengths of the data bars, either arranged horizontally or vertically, to compare the categories. Bar charts should be used instead of pie charts when handling at least 5 or more categories, as the bar chart will provide much more visual clarity for an audience to be able to interpret the differences between the lengths of the bars, rather than the constricting areas of a pie's slices. Employing a similar design method as demonstrated in Figure 2, my bar chart utilizes the browser category as its y-axis and share (usage) percentages as its x-axis, while lightly shading the smaller data bars and highlighting Google Chrome's bar of 72% in red to stand out among the rest. As well as direct the audience's attention to the central focus of the visualization that in 2024, Chrome held the lead in the most used browser across the world.

Figure 3 - Alternative Chart

References:

Kuznetsova, A. (2024, July 13). Pie charts best practices. Medium. https://nastengraph.medium.com/pie-charts-best-practices-2f8ac3b73c80

 (n.d.). What is a pie chart?. Tableau. https://www.tableau.com/chart/what-is-pie-chart

Evergreen, S. (2019). Effective Data Visualization (2nd ed.). SAGE Publications

Browser market share worldwide. StatCounter Global Stats. (n.d.). https://gs.statcounter.com/browser-market-share/all/worldwide/2024