California and Texas Absorb Nearly Half of All Household Aid Disbursements Figure 25.1 , California and Texas Absorb Nearly Half of All Household Aid Disbursements

A proportional symbol map encodes a quantitative variable as the area of a circle placed at a geographic centroid. The active perceptual channel is 2D size estimation , viewers compare circle footprints to judge relative magnitude. Because the symbol is anchored to a point rather than filling the administrative polygon, the encoding decouples visual weight from geographic area entirely. Wyoming and Rhode Island receive equally legible circles regardless of how much land each occupies.

The message is about absolute reach , how many households were served, not how many per capita or per square mile. That distinction immediately disqualifies the choropleth: choropleth shading implies proportion relative to the polygon's area, which forces viewers to mentally normalize every shade against state population or geography. That cognitive burden belongs to the chart, not the viewer. The bubble map carries it by encoding raw count directly in circle area, leaving the viewer free to compare size.

A choropleth of raw household counts would make Montana appear data-rich , large, mid-tone polygon , when its absolute count is among the lowest in the dataset. Texas's dominance would be undercut by the visual mass of vast, sparsely-populated Western states. The choropleth's failure mode here is area conflation: polygon darkness reads as magnitude, but polygon size is geographically determined, not data-determined.

framework , FT Visual Vocabulary The FT Visual Vocabulary separates proportional symbols from choropleths on exactly this axis: use a choropleth for rates and ratios bounded by administrative units; use a proportional symbol for totals and absolute counts at a centroid. The operative test , does the polygon's area carry information about the variable? If no, remove it from the encoding channel and place a symbol at the centroid instead.

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 bubble map in D3 v7. Two files:

The ideas in this chapter didn't appear from nowhere. Charles Booth mapped poverty across London block-by-block in his 1889 Descriptive Map of London Poverty , color-coding streets from "lowest class, vicious" to "upper-middle and upper class." It was the prototype for every social-data spatial visualization since. Charles Booth, circa 1895. AI-generated portrait based on a public domain photograph (Wikimedia Commons).

The ideas in this chapter didn't appear from nowhere. Charles Booth mapped poverty across London block-by-block in his 1889 Descriptive Map of London Poverty , color-coding streets from "lowest class, vicious" to "upper-middle and upper class." It was the prototype for every social-data spatial visualization since. Charles Booth, circa 1895. AI-generated portrait based on a public domain photograph (Wikimedia Commons).