The world's cities are growing far faster than its population. Indeed, aside from the growth of population itself, urbanization is the dominant demographic trend of the half-century now ending. In 1950, 760 million of the world's people lived in cities. By 1998, this had at least tripled, to more than 2.7 billion. The number projected to live in cities by 2050, some 6.2 billion people, exceeds world population today. (See Table 14-1.)1

Urbanization on anything like the scale that we know today is historically quite recent. In 1800, only one city-London-had a million people. Today, 326 cities have at least that many people. And there are 16 megacities, those with 10 million or more residents. Tokyo is the largest, at 28 million. Mexico City is second, at 18 million. Bombay, Sao Paulo, and New York

City are close behind, with 17 million each. Rounding out the list in descending size are Shanghai (14 million), Calcutta (13), Los Angeles (12), Buenos Aires (12), Seoul (12), Beijing (12), Lagos (12), Osaka (11), Delhi (11), Rio de Janeiro (10), and Dhaka (10).2