Why did urban growth occur especially quickly in Asia and Africa during the 20th century?

During the 20th century, rapid urban growth in Asia and Africa was driven primarily by two interconnected factors: high rates of natural population growth and large-scale rural-to-urban migration.12

Following World War II, many developing nations experienced a significant decline in mortality due to the introduction of modern health techniques. Because these improvements were not accompanied by a corresponding decline in fertility, populations expanded dramatically. This demographic pressure, combined with the mechanization of agriculture—which reduced the need for labor on farms—pushed increasing numbers of rural residents to seek opportunities in cities.324

In many cases, this influx of people occurred faster than cities could provide adequate infrastructure, housing, and employment, leading to the emergence of squatter settlements and shantytowns. While industrialization served as a traditional catalyst for urban growth, in many Asian and African cities, the service sector and the informal sector became the primary sources of employment for new arrivals.12