Two-thirds of the world’s population will be living in cities by 2050, the United Nations has projected, with India, China and Nigeria set to drive a surge in urbanization.

Today, around 55 percent of the world’s population is thought to be living in an urban area or city, with that figure set to rise to 68 percent over the coming decades, according to the “Population Division” report from the UN’s Department of Economic and Social Affairs.

The study, published Wednesday, also forecast a dramatic upswing in the number of megacities around the world. To date, there are 33 urban centers with populations of more than 10 million people — although this is expected to rise to 43 by 2030, mostly in developing countries.

In 1990, there were just 10 megacities worldwide.

Tokyo is the world’s largest city with a population of approximately 37 million people, followed by New Delhi with around 29 million and Shanghai with 26 million. However, India’s capital is forecast to surpass Japan’s most populous area by around 2028.

The UN said the growth of megacities was likely to stem from an accelerating shift from rural to urban-living areas around the world, particularly in Asia.

In North America, 82 percent of people were found to live in cities, compared to 74 percent in Europe. In Asia, around 50 percent of people were based in metropolitan areas, while Africa was thought to be the least urban-populated continent with only 43 percent of its population situated in cities.

However, the UN projected this trend would change over the coming decades, with India, China and Nigeria accounting for 35 percent of the estimated growth in urban populations between 2018 and 2050.

The report also highlighted the need for more sustainable urban planning and public services worldwide.