Not just 5, but India is soon going to have 7 mega cities and Delhi will continue to be the world’s 2nd most populous city till 2030, adding a staggering 9.6 million people to its population, the most in any mega city.
2016 World Cities Report issued by the UN's department of economic and social affairs has revealed these facts. Unlike using the administrative boundaries, the report has used the concept of “Urban agglomeration” which is the "the contiguous urban area, or built-up area".
For instance, the satellite cities of Ghaziabad, Noida, Faridabad and Gurgaon are included in the case of Delhi urban agglomeration. The people in these contiguous areas are economically and socially integrated with the main city and so such inclusion is touted to make sense.
About 500 million people (6.8% of the world's population or 12% of the world's urban population) live in 31 such mega cities around the world. The number of mega cities, according to report, will increase to 41 by 2030 and their population would be 730 million (8.7% of the world's population).
Mumbai, Kolkata, Bengaluru and Chennai are the other Indian cities figuring in 2016's mega cities list and by 2030, Hyderabad and Ahmedabad will join the list, as their respective populations would cross 10 million.