“Aztec peasants, Babylonian shepherds, Athenian stonemasons, and Carolingian merchants spoke different languages,2 wore different clothing, and prayed to different deities, but they all ate the same amount of food, lived the same number of years, traveled no farther—or faster—from their homes, and buried just as many of their children. Because while they made a lot more children—worldwide population grew a hundredfold between 5000 BCE and 1600 CE, from 5 to 500 million—they didn’t make much of anything else. The best estimates for human productivity (a necessarily vague number) calculate annual per capita GDP, expressed in constant 1990 U.S. dollars, fluctuating between $400 and $550 for seven thousand years. The worldwide per capita GDP in 800 BCE3—$543—is virtually identical to the number in 1600. The average person of William Shakespeare’s time lived no better than his counterpart in Homer’s.”
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William Rosen,
The Most Powerful Idea in the World: A Story of Steam, Industry, and Invention