Dissecting Pie Charts.

Pie charts can be regularly found both in the popular media and research publications. There is evidence that other forms of visualizations make it easier to evaluate the relative order of the data items. Doughnut charts have been suggested as a variation that has advantages over pie charts. We investigated how pie charts and doughnut charts are affected by the number of sectors in the chart, the difference in sector sizes, and the size of the hole. We carried out an eye tracking study to find out how the charts are read. Our study reveals the distribution of visual attention for each type of chart. The results indicate that doughnut charts with a medium size hole have a slight edge over the other chart types we studied. We also show that contrary to common claims, for information extraction also the area and length of sector arc are used in addition to the angles of the sectors.