We live in an urban world. Half of the world's population already lives in cities, generating more than 80 percent of global GDP today. But the urban economic story is even more concentrated than this suggests. Only 600 urban centres, with a fifth of the world's population, generate 60% of global GDP. In 2025, we still expect 600 cities to account for about 60% of worldwide GDP - but the cities won't be the same. The earth's urban landscape appears to be stable, but its centre of gravity is shifting decisively, and at speed. Companies trying to identify the most promising growth opportunities need to be able to map this movement and spot the individual cities where their businesses are most likely to thrive.