As of 2009, more than half of the
world’s population lived in urban areas.
Urbanization is commonly associated
with mega-cities (cities with over 10
million inhabitants), but the majority
of the world’s urban population lives
in cities with fewer than 500,000
inhabitants.7
The United Nations Population
Division projects that the global urban
population will almost double from
3.5 to 6.3 billion by 2050 (Figure
1), assuming that fertility rates decline