The Georgia Negro: A Social Study - Diagram shows value of taxable property owned by African Americans in Georgia between 1875 and 1890 [LCCN2013650442]
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 tree-ring metaphor does something a bar chart cannot: accretion. Each year physically encloses the years before it, so decline is not even representable in the form - the argument that progress was continuous is built into the geometry. Because the bands encode value as radius but read as area, the later years feel far larger than the ratios justify, which is the rhetorical point. The ragged dagger callouts and their irregular angles are what stop the plate from being a diagram: they force the eye to travel, they break the circle's symmetry, and they make the reader work for each figure, which slows the plate down and holds a standing viewer.
Steal this when
Use this when cumulative total is the story and you need the audience to feel that the base has never given ground. Concentric bands beat stacked bars whenever the point is that each period is added to, not compared against, the last.