"By 2020, Tokyo's population is projected to begin to decline, while Delhi is projected to continue growing and to become the most populous city in the world around 2028," the report said.The projected population size of New Delhi in 2028 is about 37.2 million, surpassing Tokyo's 36.8 million, it added.By 2030, the world is projected to have 43 megacities with more than 10 million inhabitants, most of them in developing regions.
The global rural population is now close to 3.4 billion and is expected to rise slightly and then decline to 3.1 billion by 2050.
Integrated policies to improve the lives of both urban and rural dwellers are needed, while strengthening the linkages between urban and rural areas, building on their existing economic, social and environmental ties," it said.
By 2050, it is projected that India will have added 416 million urban dwellers, China 255 million and Nigeria 189 million.Tokyo is the world's largest city with an agglomeration of 37 million inhabitants, followed by New Delhi with 29 million, Shanghai with 26 million, and Mexico City and S o Paulo, each with around 22 million inhabitants.
Most of these are located in the low-fertility countries of Asia and Europe where overall population sizes are stagnant or declining.