Cities as permanent and static may be a Western fact, but it is an Indian myth. After 20 years in India, I went back to Philadelphia where I had been a student. Despite the long break, I was able to move about familiar buildings and landmarks as if I had just left yesterday. I return to Delhi after a month away, and the change is noticeable and disorienting. Buildings have stained, broken, changed ownership, added floors, been demolished. The park has acquired a temple, families are camped on the road. There are more people everywhere.

Demographic changes to the city are far more caustic and lethal than those that meet the eye. In Mumbai, 2,400 migrant families move in every week; while Delhi gets its share with a two lakh intake every year. If the crowding is more visible in Mumbai it is only because Delhi's 1,500 square kilometres spreads the increase over a wider footprint. In cities like Visakhapatnam, Kanpur and Jabalpur more than half the residents live in large slums or as migrants waiting to make their own slums. More enter every city every day.