It’s also a strangely localized and temporary phenomenon. At any one time, there is usually one part of the world where innovation flourishes best, attracting talent from all over: California in 1960, the U.S. East Coast in 1920, Britain in 1800, Holland in 1650, Renaissance Italy in 1500, Song China in 1000, Abbasid Arabia in 800, ancient Greece in 500 B.C., the Ganges Valley before that. These were places that were relatively wealthy, free and open to trade at the time.