Multiple Pie Charts: Unreadable, Inefficient, and Over-Used

Abstract

A pie chart is a common way of presenting simple statistics—for example, the amount of time devoted to teaching, researching, and administration by the faculty can be illustrated by dividing a circle (‘pie’) into three appropriately sized segments. There has been much discussion about the strengths and weaknesses of such pie charts for a long time, and it is not likely to end soon. 3D pie charts show the same statistics, but in three dimensions. Multiple pie charts can be found where the data for groups to be compared are presented in adjacent pies. Here we argue that, even if a simple pie chart may have some advantages, the same cannot be said for multiple pie charts. Multiple pie charts are difficult to analyze and interpret, especially when comparing adjacent pies.