The Cost of Pie Charts

Visualization of proportions is a very common need and there are many techniques for it. The pie chart is popular among practitioners and general audience, but many prominent experts advise against using it. This paper reports an experiment where the pie chart is compared to stacked bar charts with a baseline condition of table. The aim is to study if the performance differences justify the bad reputation of pie charts. In the experiment the participants were requested to list out the elements of a visualization in descending order of size. The task time and the answer were recorded. The results show that the pie chart is slower and less accurate than the stacked bar chart, especially when the difference between the elements is small, but the participants find it slightly more pleasant to use. The participants also perceive the stacked bar chart as the most effective visualization.