I am intruiged with a new craze that seems to be gathering momentum in how data is represented. Until a month ago I couldn’t remember when I last saw relative areas of circles used to compare quantities, but recently it seems to be all over the place. I think that the first one I saw was on the BBC (here) and there it felt quite clever since it used the edges of the huge circles to show the sense of scale of GDP without swamping the rest of the data :-
Succeeding charts that I have seen seem to have no logic in their use of circles – just using the same meme. Of course, as I write this, I am struggling to refind the things I had seen amongst the deluge of news items on the markets. But, there’s an example from the Daily Mail (here). As I look at it again, I think it uses a slightly different model of showing spheres and using the relative volumes .. but that’s based on eyeballing it rather than measuring it. EDIT And, not helped by the scale which seems to change from institution to institution. When I saved this post I found that the second section was missing, and was in fact a seperate image file. I’ve now added that, keeping both images a their natural size (apols that it makes formatting dreadful). Done that way the scale appears to be consistent between the two images. When they appeared, at least on the web, theyu were auto-scaled to fit the column that they were in, and that made the relative scales wrong – shows one of the unintended hazards of web publishing!
Greg Pyes blog 