At the start of the 20th century, 1 out of 8 people in the world lived in urban areas, and by the 1950s, it was nearly 1 in 3. Now, it is 1 in 2. In the coming decades, virtually all population growth will be in urban areas. In East Asia, the urban population is expected to increase by about 450 million people over the next two decades, meaning that a city the size of Paris will be added every month.
In South and Central Asia, the increase is expected to be nearly 350 million, and in Sub-Saharan Africa almost 250 million. Yet unlike the industrialized world where urbanization unfolded over many decades (thereby allowing public and private sector institutions to mature gradually), the process in developing nations is far faster and is unfolding against a backdrop of rapid population growth, lower incomes, and fewer opportunities for international migration.
While urbanization is a long-studied concept, it remains poorly understood. For increases in population density give rise to social, environmental and administrative challenges that are easily recognizable, such as public sanitation problems, inadequate supplies of formal housing, traffic congestion and crime. In other words, the “costs of grime, time and crime”.