How the cities grow

Posted: 26 January 2008

The world's rural population has reached its peak, and almost all further population growth will be absorbed by urban settlements. By 2008, for the first time in human history, half the 6.6 billion people of our planet are living in towns and cities.

Estimated and projected urban population in the world, 1950-2030. Source: UN, 2002.

That is a huge change. In 1950, only 29 per cent of the world's population of 2.5 billion were urban dwellers. And 83 per cent of the developing world's people were still living on the land. By 2030 over 60 per cent of the world's 8.2 billion global citizens will be living in towns and cities.

While attention is often focused on the world's biggest megacities such as Sao Paulo and Mumbai (Bombay), they contain only a relatively small proportion of all urban dwellers. Today, only about 15 per cent of urban dwellers live in cities with more than 5 million people, while over 60 per cent live in towns and cities of one million or fewer.

Nor is the proportion likely to change much. The UN projects that by 2030 16 per cent of the urban total will be in cities with over 5 million people.

Three-quarters of the world's anticipated population growth in the next 30 years will take place in relatively small cities with populations of between 1 and 5 million.

In fact, the speed of growth in most megacities slowed during the 1980s, so that some of the early projections have had to be drastically revised. In the early 1970s, for example, the UN projected that Mexico City would grow to over 31 million by the year 2000. In fact its population had only reached 18 million by 2000.

Others cities where estimates for end of century numbers had to be scaled down include Rio de Janeiro (from 19.4 to 10.7 million), Calcutta (19.7 to 13.1), Cairo (16.4 to 10.4) and Seoul (18.7 to 12.3). Other projections have proved more accurate, as in the case of Bombay (Mumbai), whose population in 2000 was over 16 million.

Traffic in Phnom Penh, Cambodia. Credit: FAO

Overall the picture is a mixed one. Some of the 30,000 urban centres in the South grew very fast in the 1980s, some grew rapidly and many grew slowly or not at all. In general, the greatest growth took place where economic activity was most buoyant, as in China.

What is unprecedented, is the number of countries which are rapidly urbanising and the number of cities that are growing rapidly. Many of today's million-plus cities have seen numbers grow tenfold in 40 years. These include places such as Amman, Curitiba, Dar es Salaam, Dhaka, Khartoum, Lagos, Nairobi and Seoul.

Also without precedent is the appearance of the huge agglomerations, never experienced before. In 1940, only New York and London had more than 5 million people. By 2005 there were 50 cities with over 5 million people of which 20 had over 10 million. Eleven of these larger megacities are in Asia.

Related links:State of the World's Cities Report 2001.The Challenge of Slums: Global Report on Human Settlements 2003.World Urbanization Prospects: The 2005 Revision.

This section has been prepared with the generous assistance of Robert Livernash, Senior Editor at the World Resources Institute (WRI) in Washington and David Satterthwaite, Director of the Human Settlements Programme at the International Institute for Environment and Development in London.