Album de statistique graphique de la Ville de Paris - sheet 6 of 12 (BnF btv1b52505495j)
The pattern
This still is filed under Data as proof.
Define
A chart, map, or count that is the argument, not an illustration next to the argument.
Mechanism
Sighted evidence. The reader is asked to believe their eyes: a bar, a share, a spread on a map.
Verdict
The claim is comparative or quantitative and the figure can be read without a caption doing the sell.
Why it works
This is a deliberate before-and-after pair executed as two physical sheets, and every design decision serves that: identical projection, identical symbol geometry, identical colour assignment, identical legend layout. Because the encoding is held completely still, any difference the eye picks up between the two plates is a real difference in the data, which is the whole point of a controlled comparison. The legend text is trimmed rather than restructured, so the reader's second pass costs almost nothing. Keeping the exact figure under each circle means the reader can convert a vague impression of growth into a number without a third document.
Steal this when
Use this whenever two scenarios, two years or two territories have to be compared and you control both renderings. Hold every visual variable fixed except the one carrying the data, and put the two views on facing pages rather than overlaying them.