I'm absolutely bewildered by their "curvatures" chart: > How to read the chart > Each group of lines is a country > Each line is a year > The position of th

I'm absolutely bewildered by their "curvatures" chart: > How to read the chart > Each group of lines is a country > Each line is a year > The position of the curvature along the line indicates the top category by year Uh...what? Vertical position of a bend on a line tells you...the...category? What? Why? Why did they do this? It makes no sense to me at all.