The Georgia Negro: A Social Study - Graphs show number of African American owners and the value of their property in Savannah and Georgia between 1880 and 1899 [LCCN2013650443]
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
Turning the second measure ninety degrees lets two incompatible units - people and dollars - share one field without a second axis or a dual-scale cheat, and the crossing point becomes composition instead of collision. Colour is locked to city across both orientations, so the reader learns the code once and can then read either direction. Setting the values inside the bars removes the need for a value axis entirely, which is why the sheet stays empty enough to see the shape.
Steal this when
Use this when you must show two incommensurable metrics for the same entities and refuse a dual axis - run one set horizontally, the other vertically, and hold colour constant as the entity code.