2001 Census conducted enumeration of slum population for the first time in the country. The Census of India, 2001 conducted the enumeration of slum population of 640 cities/towns with a population of 50,000 or more spread across 26 States/ Union Territories. This enumeration reported slum population of 42.6 million constituting 23.1 percent of the population of 640 cities/towns.
