Those who design the graphics in research survey reports like to mix in some plots that convey their data by the relative size of an object. Size here actually means the area of the object, and the object is typically a circle. Clifford Chance AsiaMA 2017 [pg. 6] offers a plain vanilla example, just proportional circles, no colors, visible data arranged from largest to smallest. The area of the left circle almost doubles the area of the circle to its right — just as 48.7\% is almost twice 26.4\%.
Pinsent Masons TMT 2016 [pg. 20] also arranges the circles in declining order of area. The labels underneath with extender lines show one technique for including additional information. Unlike Clifford Chance, which left the circles uncolored, Pinsent Masons shaded them grey and switched the font color to white. The design feature, the curvy line on the left in the shape of a reverse “L,” is in the snippet to show the relative size of the area plot and its location at the bottom right of the page (from the location of the page number).
The final example, from DLA Piper RE 2017 [pg. 10], has four less-than-conventional features. Fanciful cityscapes show through in the larger circles like a watermark. Second, the plot unnecessarily outlines the larger circle; you should want readers to focus on the relative sizes of the inner, darker circles. Third, most readers will fix their eyes first on the prominent “1”, “2”, and “3” rather than on the meaningful percentages below them in parentheses — which do not even have a percentage symbol. Finally, the graphic truncates the circles at the bottom, which seems particularly odd since the area of the circles is meant to convey the differences in percentages between the cities.