Can someone explain to me what the x-axis means in the "Divorce Rate By Occupation" chart? It seems to be just a random distribution from -1 to 1, because the author wanted to use dots to represent each title. I suppose that's a very space-efficient way of representing the data, but it's also pretty tedious to have to mouse over everything, and it doesn't work well on a small screen.

Might have been better just to put this in a list.