GDP
The world as a whole has not had the sixteen-fold multiplication of its material prosperity seen in the United States over the past century. Only 12% of the world’s population lives in countries where GDP per capita at the start of the third millennium was more than $20,000 per year.
The average inhabitant of Thailand of Tunisia today has about 3 times the productive potential of the average inhabitant of the United States in 1900; and the average inhabitant of Argentina, Botswana, Uruguay, or Mexico has 5 times the material productive potential of the average inhabitant of the U.S. in 1900.
Perhaps 36% of the world’s population in 2000 lives in a country with a level of material output per capita less than that of the United States in 1900. Angus Maddison estimates that world per capita GDP at the end of the 20th century is 5 times what it was at the century’s start — and Maddison’s estimates make insufficient allowance for technological change and the invention of new commodities.
The 19th century saw perhaps a doubling of measured material standards of living in the United States — perhaps a tripling once proper account is taken of the impact of new technologies. The standard of living in the Netherlands, probably the richest economy in the world at the end of the 18th century, might (or might not) have been some 50% higher than it had been three centuries before.
Medieval historians speak of centuries and half-millennia when they speak of the pace at which key inventions diffused across the landscape.
“Cornucopia: Increasing Wealth in the Twentieth Century” by J. Bradford DeLong