Honest Charts

A chart can be accurate in every number and still mislead. The commonest trick is a truncated axis: start a bar chart at 80 instead of 0 and a gap of 4% looks like a gap of 400%. Bar length is the message, so bar charts must start at zero. Line charts may start elsewhere, because they show change, not length, but say so clearly.

Other traps: choosing a scale that flattens or exaggerates a trend, leaving out units, comparing charts that use different ranges, and using 3D effects that distort size. Before you publish a chart, ask whether someone who only glances at it would draw the same conclusion as someone who reads every number.