This was extremely helpful. Clear, and well done, too. If you're looking for criticism, I'd say that you should consider moving the last paragraph on the first page. When I was reading it, I stopped reading that paragraph several times and referred to the picture below, and I felt confused because I was jumping around trying to look at it and read the paragraph above it at the same time. After you finish the paragraph, everything is clear, but it might go more smoothly for the reader if you lead to the graphic with the first sentence: "Here are some examples of these differences, and they are striking." Then the graphic, and move the full explanation of the graphic below. I think people are used to referring back to something they've seen earlier and do that more naturally than referring to a graphic below the paragraph they are reading.
Take it or leave it - it's a small point.