The Georgia Negro: A Social Study - Occupations of Negroes and whites in Georgia
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
Sharing one pivot forces a direct angular comparison that two separate pie charts could never deliver - the crimson wedges nearly mirror each other, so the eye registers the similarity before it reads a single word. Once that similarity is established, the small slices are where the argument lives, and they are the ones that differ most. Splitting the legend into two margins keeps the centre uncluttered and makes the mirrored geometry the first thing you see. Colour is held constant across both fans so the reader learns the code once.
Steal this when
Use this when two groups are assumed to differ and your point is that they mostly do not, apart from one specific asymmetry. Mirror them on a shared pivot at the same scale, let the big shared slice establish the parity, and let the small slices carry the argument.