Over 55 percent of Indians will live in urban areas by 2050, a big change from now when only about 30 percent of the country's population is urban, according to projections in a United Nations report.
However, India will still not be as urbanised as China where the number of people living in cities will go up to 70 percent from the current 40 percent.
India will remain the country with the largest rural population during most of the future decades, according to the 2007 Revision of World Urbanisation Prospects released by the UN Tuesday.
By 2025, Chennai will be another mega city of over 10 million people, besides Mumbai with 26.4 million (up from 18 million in 2005), Delhi at 22.5 million (up from 16 million) and Kolkata with 20.5 million residents (up from 14 million).
The population growth in many second tier cities will even be higher. In Ahmedabad by 2025, the population will grow to 7.7 million, up 50 percent from the current 5.1 million. In Pune, 6.8 million people will live by then, a growth of 60 percent from the current 4.4 million.
Migration from rural to urban areas would continue despite attempts by the country's planners to prevent people from moving to cities, said Hania Zlotnik, director of Department of Economic and Social Affairs' Population Division, while releasing the report in New York.
Zlotnik said Indian planners should try to promote economic development in rural areas. But improving agriculture and establishment of agro-industries would mean fewer people would be needed in that sector, pushing excess labour to the non-farm sector in the cities.
She outlined two scenarios - either people would migrate to cities such as Mumbai, or one-time rural areas would transition into urban centres by generating other activities as has been happening in China.
The annual population growth in India's rural areas has been declining since reaching a peak of 1.9 percent during 1980-85. It will record negative growth by 2025. In comparison, the urban growth rate reached a peak of 3.9 percent during 1975-80 and has been declining since, yet will remain above two percent till 2040.
Projecting for the world, the UN report said half the global population would live in cities by the end of this year, for the first time in human history. Their number would rise to 70 percent by 2050, most of that growth being concentrated in Asia and Africa. The number of mega cities is expected to double from the current 20 to 40 by year 2025.
The greatest expansion, however, would happen not in metropolises but in cities with populations of less than 500,000 and even some of the rural areas will graduate into urban areas.
The report notes that its projections will be realised only if fertility rates in the developing world continue to decline.