The case for a clean revolution

By 2050, our planet will be home to 9 billion people. The world’s middle class will reach 4 billion; by 2020, 50 percent of China’s population will be middle class. The world has also become increasingly urban: In 1800, only 2 percent of the world’s population was urban. Today, half of the world’s people are living in towns and cities, with 180,000 people added to the urban population each day.

Related Subject(s): Economic and Social Development