This is a very interesting chart. It shows the percent of the world’s GDP as represented by Britain, the US, China, and the USSR since 1820 (pre-USSR Russia is considered part of the USSR for some reason, but not post-USSR Russia, and Britain is cut off circa 1950—gee, I wonder why?).

What is most interesting to me is that the line between Britain and the US intersects circa 1913. Furthermore, look at how America’s steady incline begins to peter out after that time. It’s almost as if a tiny pinprick had been made in a balloon, or a deadly parasite had set upon a healthy host.