North America + East Asia hold 62 percent of global AI for Good investment Figure 56.1 , North America + East Asia hold 62 percent of global AI for Good investment

A Proportional Area Chart encodes quantitative values as the area of geometric shapes , most commonly circles, but any closed shape works. The perceptual mechanism is area estimation : the eye reads the space inside the shape and compares it across items. Area estimation is less precise than position on a common axis (the bar chart's mechanism), which makes proportional area charts better suited to presentational contexts , conveying the scale of differences at a glance , than to analytical ones, where readers need to extract specific values.

The data spans 43:1 from the largest to the smallest value ($8,420M to $195M). A bar chart would render this honestly but the smallest bars would be barely visible without a log scale, which introduces its own perceptual problems. A proportional area chart handles extreme ratios naturally: the eye tolerates wide size variation between circles and still perceives the relative scale. The circular form also avoids implying a ranking or sequence , these are independent regions, not ordered categories.

the common mistake If you set radius ∝ value instead of area ∝ value , area grows as value². North America ($8,420M) is 43times larger than Oceania ($195M). With correct area encoding: visually 43times larger area . With radius encoding: visually 1,849times larger area . The error amplifies differences by a factor equal to the value ratio. Hit the radius error toggle on slide 1 and watch the small circles become nearly invisible.

The one decision worth knowing: circle color uses the same sequential scale as the size (darker = larger value). This is double encoding , both area and colour encode the same variable. That's usually redundant and inefficient; here it is deliberate. Double encoding reinforces the size hierarchy for viewers who find area estimation difficult, and it makes the smallest circles (which are almost invisible by area) still perceptible by hue contrast.

FT Visual Vocabulary + Tufte FT Visual Vocabulary: Magnitude , Size comparison . Abela quadrant: Comparison , comparing the relative magnitude of items without a continuous axis. Tufte: proportional area charts sacrifice data-ink ratio precision for gestalt comprehension; acceptable only when the scale of difference is the message, not the precise values.

Paste this into Claude Code to generate a working version of this chart, plus its data file. The result will not be a perfect replica , the goal is that the reader can run the prompt, get a chart of this type, and read its source. Generate a complete, self-contained proportional area in D3 v7. Two files:

The ideas in this chapter didn't appear from nowhere. Joseph A. Hill served as Chief Statistician of the U.S. Census and oversaw the Statistical Atlas of the United States editions of 1900, 1910, and 1920 , produced with the Census Office's graphics team. Those atlases pioneered the use of proportionally-sized squares, circles, and human figures to encode population, immigration, manufacturing output. Every modern bubble-area chart is a descendant of those plates. Joseph A. Hill, circa 1920. AI-generated portrait based on a public domain photograph (Wikimedia Commons).

The ideas in this chapter didn't appear from nowhere. Joseph A. Hill served as Chief Statistician of the U.S. Census and oversaw the Statistical Atlas of the United States editions of 1900, 1910, and 1920 , produced with the Census Office's graphics team. Those atlases pioneered the use of proportionally-sized squares, circles, and human figures to encode population, immigration, manufacturing output. Every modern bubble-area chart is a descendant of those plates. Joseph A. Hill, circa 1920. AI-generated portrait based on a public domain photograph (Wikimedia Commons).