The map makes it clear that the global rconomy takes shape around perhaps 20 great Megas scattered throughout the world. These regions are home to just 10 percen of total world population, 660 million people, but produce half of all economic activity, two-thirds of world-class scientific activity, and three quarters of global innovations. The great urbanologist Jane Jacobs was the first to deescribe why megalopolises grow. When people migrate to one place, they all become more productive. And the place itself becomes much mor productive, because collective creativity grows exponentially. Ideas flow mor freely, are honed more sharply, and can be put into practice more quickly.