This interactive world map of urbanization trends created by The Economist tracks global city population shifts and forecasts from 1950 until 2030.  The visualization is based on data from the United Nations' Population Division of the Department of Economic and Social Affairs.

Users can watch population shifts over time, double-click a country to zoom in, or use the search box to hone in on a city and see a graph of its population over time.

The map shows that more people now live in urban areas than in rural areas (54 percent vs. 30 percent in 1950).  This shift has been accompanied by the rise of the megacity: these massive urban centers housed only 0.9 percent of the world population in 1950, but the United Nations projects that 9 percent of the world population will live in 41 megacities (particularly in Africa and Asia, where urbanization is taking place rapidly) in 2030.



The United Nations report concludes that

"As the world continues to urbanize, sustainable development challenges will be increasingly concentrated in cities, particularly in the lower-middle-income countries where the pace of urbanization is fastest.  Integrated policies to improve the lives of both urban and rural dwellers are needed."

Read more:
http://www.economist.com/node/21642053
http://esa.un.org/unpd/wup/

TeachingwithData.org resources:
Increasing Urbanization (http://www.teachingwithdata.org/resource/3858
The Social Structures of the Cities (http://www.teachingwithdata.org/resource/3186)
Social Explorer (http://www.teachingwithdata.org/resource/3914)
Before and After 1940 (http://www.teachingwithdata.org/resource/3859)
A Decade of State Population Change (http://www.teachingwithdata.org/resource/3860)
Census Flow Mapper (http://www.teachingwithdata.org/resource/3844)