Compiled by Samuel K. Moore and Alan Gardner
By 2008, for the first time in history, half of the world's population will live in urban areas. By 2030, 4.9 billion people, or 60 percent of the world population, will be urban.
In 2005, megacities accounted for 9 percent of the world's US $59.4 trillion gross domestic product. Five megacities—Los Angeles, Mexico City, New York City, Osaka-Kobe, and Tokyo—were among the world's 10 richest. Those five combined were more than twice as rich as the other 15. GDP will grow on average 4.9 percent per year across 22 megacities by 2020, when their combined GDP will reach $9.4 trillion. NOTE: ALL GDP USES THE PURCHASING POWER PARITY METHOD.
Since 1975 the number of urban agglomerations with a population of 10 million or more—megacities by the United Nations’ definition—grew from just three to 20. By 2015 two more cities, Istanbul and Guangzhou, will cross the 10 million mark. Megacities account for 9.4 percent of the world’s urban population. The growth of megacities is predicted to slow over the coming decade, and in 2015 they will still account for nearly the same proportion of the urban population that they do now.
In the face of this GDP growth, the world slum population could swell from 998 million in 2005 (estimated) to 1.4 billion in 2020, assuming efforts to stem this growth do not succeed. In four of the 10 countries with the highest slum populations in 2001, slum dwellers made up a majority of the urban population. Except for Iran, each of the 10 contained at least one megacity.
Particulate matter smaller than 10 micrometers in diameter (pm10) is the most dangerous to human health, because it can pass through the nose and throat and enter the lungs—leading to asthma, lung cancer, cardiovascular problems, and premature death. Of the megacities, Karachi, Pakistan, had by far the worst pm10 problem in 1999, the last year for which complete data were available. New York City had the cleanest air.
Some large megacities in the developing world have done a better job at providing a connection to the electric grid than to the sewage and water systems. The United Nations has gathered such data on only eight of the 15 developing world megacities.
Among the 50 highest capacity international city-to-city Internet routes in 2006, 12 connect to megacities—New York City, Tokyo, Los Angeles, and São Paulo (listed in order of bandwidth). Those 12 connections combined carried up to 924 gigabits per second of data. At 387 Gb/s, the London�to�New York connection is the highest capacity in the world.