It's a fundamental shift that may be altering the very fabric of human life, from the intimate, intricate structures of individual families to the massive, far-flung infrastructures of human civilizations. In 1950, fewer than 30 percent of the world's 2.5 billion inhabitants lived in urban regions. By 2050, almost 70 percent of the world's estimated 10 billion inhabitants – or more than the number of people living today – will be part of massive urban networks, according to the Population Division of the United Nations' Department of Economic and Social Affairs.
These staggering statistical trends are driving the evolution of the "megacity," defined as an urban agglomeration of more than 10 million people. Sixty years ago there were only two: New York/Newark and Tokyo. Today there are 22 such megacities – the majority in the developing countries of Asia, Africa, and Latin America – and by 2025 there will probably be 30 or more.
Consider just India. Though the country is still largely one of villagers – about 70 percent of India's 1.2 billion inhabitants live in rural areas – immigration and internal migrations have transformed it into a country with 25 of the 100 fastest-growing cities worldwide. Two of them, Mumbai (Bombay) and Delhi, already rank among the top five most populous urban areas.