For most of human history, people have been poor. From one generation to the next, the norm was a subsistence level of existence. Over the past three thousand years, according to the economic historian Angus Maddison, there was almost no change in global per capita income—until about two hundred years ago. The average person living on the planet in 1500 B.C. would have had a similar living standard to someone in 1500 A.D. Of course, there were incremental improvements in technology in the intervening centuries. Bronze gave way to iron. Farming techniques improved. But the resulting rises in output were offset by increases in the population overall. As the academic Gregory Clarke has put it, “sporadic technological advances produced people, not wealth.” Or as an economist might say, growth tended to be extensive, rather than intensive.

Human kind was stuck in what we call the Malthusian trap. With a few very rare exceptions, we only escaped from it remarkably recently—ironically, more or less at about the date Thomas Malthus published his spectacularly ill-timed Essay on the Principle of Population in 1798. Up until about that moment, Malthus’s basic premise—that any increase in resources would result in a corresponding rise in the population, which would then cause shortages—had been essentially correct.

The past few centuries have seen a great escape from the Malthusian trap.

Instead, over the past few centuries, we have seen a great escape from the Malthusian trap. Output has increased significantly faster than the