Album de statistique graphique de la Ville de Paris - sheet 2 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
The proportional-circle family carries two levels at once, the diameter of each circle stating the species against the total while the wedges inside state which abattoir handled it, so a hierarchy and a breakdown share one figure without a second chart. Printing the exact count above each circle admits that area is hard to judge precisely and repairs it, which is the correct way to use an area encoding rather than pretending it is readable. Carrying the same rose and mustard pair across the oyster chart, the circles and the two lower column charts binds four unrelated figures into one sheet by palette alone. Repeating the value scale on both the left and right edges of the wide column chart removes the long horizontal eye-travel that normally makes wide charts unreadable.
Steal this when
Use the circle family when a total must be broken into a few very unequal categories and each category itself needs a secondary split, the classic revenue by product line then by channel. Print the real number beside every circle, and repeat the axis on both sides of any chart wider than the eye can track.