Although a majority of developing-country urban growth will be found in
cities of less than 5 million people, it is also the case that population growth in
cities over 5 million in population is more rapid than growth of smaller cities
(under 500,000) in the developing world. In fact, according to the UN, by 2025,
only about half the urban population will be in cities with less than a half million
people, the lowest fraction ever. Moreover, the developing world is also
coming to dominate the world’s largest cities, including the megacities with
over 10 million inhabitants. Figure 7.4 provides a map locating megacities, the
largest cities in the world containing a population of at least 10 million people.
As the figure shows, in 1975, there were only 3 megacities, but by 2009, there
were 21 such metropolises. Of these 21, two-thirds were located in the developing
world. By 2025, only 5 of the 29 largest cities will be in high-income countries.
Moreover, as Figure 7.5 shows, almost all of the increments to the world’s
population will be accounted for by the growth of urban areas as migrants continue
to stream into the cities from rural areas and as urbanization rates in the
developing world continue to approach those of the developed world.
A central question related to the unprecedented size of these urban agglomerations
is how these cities will cope—economically, environmentally, and politically—with
such acute concentrations of people. While it is true that cities