Packed circle charts, just like pie, donut, and Voronoi charts, are another alternative that uses circular sections to represent parts of a whole. Since the layout of this chart consists of tangent circles placed next to each other, extra empty space appears within the main circle—space that doesn’t actually exist—causing possible perceptual errors in whole-to-part comparisons. Therefore, the packed circle chart should only be used when the focus is on comparing values at the same level.