Employment and educational opportunities are the main attraction of urban centers. But people, who hope to find a better life there, are often disappointed, as overpopulation puts a huge strain on cities' infrastructures and their ability to provide basic necessities - like clean water and decent housing.
The staggering rate of urbanization of the 20th and 21st centuries creates its own problems, esp. in developing nations, where the majority of the megacities can be found. The three fastest growing cities of the world are: Mumbai / Bombay (India), Tokyo (Japan) and Lagos (Nigeria).
Many rural migrants who come to Mumbai fail to find adequate work, and therefore cannot afford decent housing. Nearly everywhere, where a spare piece of land is available in Bombay, slums emerge along the side of train tracks and highways, and even on sidewalks. Many say addressing land and housing issues should be the city's top priority. The World Bank says 54% of Bombay's 15 million residents live in slums. The problem of slums caused by migration is shared by India's other two megacities, New Delhi and Kolkata / Calcutta, as well as urban centers throughout the developing world.
Megacity researches argue, that the demands of transport, improved housing for slum residents, environmental protections and other issues must all be addressed together in order to meet residents' needs.
Resource: City Mayors Society