“But Marx and Mill were wrong. The problems of the demographic transition turned out, in the long sweep of things, to be easy presuming successful development and income growth: They solved themselves within two generations after girls attained the leisure to learn how to read.

It was, rather, the problems of technological and institutional development and transfer that turned out to be the nastiest and most stubborn ones for the Global South. The U.S. was about twice as rich as China and India in 1800. It was 30 times as rich as they were at purchasing power parities come 1975. And, at least according to Hans Rosling and company, China and India were no richer in 1975 than they had been in 1800.

Why should this be the case in a world in which the technology was embodied in large hunks of metal shaped in the machine shops of Lancashire–hunks of metal that could be cheaply transported all over the world? Why did the 20th century see a world sharply divided between a Global North and a Global South, with productivity in the Global North growing at 2% per year while the Global South fell further and further behind?”