The world’s urban population today is around 3 billion people¹ ― the same size as the world’s total population in 1960. During the 20_th century, it increased more than ten-fold, and close to 50 percent of the world’s population now lives in urban centres, compared to less than 15 percent in 1900.² Many aspects of urban change during the period 1950―2000 were unprecedented, including not only the world’s level of urbanization and the size of its urban population, but also the number of countries becoming more urbanized and the size and number of very large cities. During these same 50...

Two aspects of the rapid growth in the world’s urban population over the last 50―100 years are the increase in the number of large cities and the historically unprecedented size of the largest cities (see Table 3). Just two centuries ago, there were only two “million-cities” worldwide (i.e. cities with one million or more inhabitants) ― London and Beijing (then called Peking). By 1950, there were 85; by 2000, 387. A large (and increasing) proportion of these million-cities are in Africa, Asia and Latin America (see Table 3).

The average size of the world’s largest cities has also increased dramatically....

Although urbanization is acknowledged as one of the most significant changes taking place within low- and middle-income nations, there is surprisingly little detailed study of what causes or influences its scale and nature within each nation. Urban population statistics can show which urban centres grow rapidly (or grow slowly, stop growing or shrink), but they tell us nothing about why.

Understanding what causes and influences urban change within any nation is complicated. Consideration has to be given to changes in the scale and nature of the nation’s economy and its connections with neighbouring nations and the wider world economy; also...

Few large cities had their initial urban expansion guided by a rational plan ― or if it was, it only applied to parts of the expansion, or its guidelines, rules and norms were only partially applied. The many factors that influenced the location and initial development of cities were noted earlier, including the availability of water, good location on transport routes (where river or sea transport may be important), the location of government (government agencies and employees as potential sources of demand for goods and services), a healthy climate, rich agricultural lands and, especially in the past, defence. But the...

All the above may be taken to imply insuperable problems for expanding cities and for the global environment. Box 4 highlights how cities actually have large potential advantages for ensuring universal provision of infrastructure and services, keeping down waste levels, re-using waste streams and delinking a high quality of life from high levels of resource consumption (and greenhouse gas emissions).

The high densities and large population concentrations in cities usually lower the costs per household and per enterprise for the provision of infrastructure (all-weather roads and paths, piped water, sewers, drains, electricity) and services (including day care, all forms of...

The world will certainly be more urbanized in 10―15 years time, and will have more large cities, but perhaps less than current projections suggest. There are good grounds for questioning whether most of the world’s urban population will live in large cities. In most high-income nations and many middle- and low-income nations, more dispersed patterns of urban development are evident. In addition, in high-income nations, much of the rural population is, in effect, urbanized rural dwellers. They receive the infrastructure and services that used to be associated with urban centres, most do not work in agriculture and many work in...