Ballooning Urbanisation

In 1800 only about 2 percent of the world's population lived in urban areas. In only 200 years, the world's urban population has grown from 2 percent to nearly 50 percent of all people. At the beginning of the 20th century some 250 million people lived in cities – only about 15 per cent of the world’s population. At the end of century, nearly half of the 6000 million people on the planet lived in urban areas.

The most striking examples of the urbanization of the world are the megacities of 10 million or more people. In 1975 only four megacities existed; in 2000 there were 18. And by 2015 the UN estimates that there will be 22.