The World’s Most Populous City Builds Mass Transit

Ranking cities by population require some choices: in particular, do you focus only the legal boundaries of the city, or on a metropolitan area? If it’s a metropolitan area, how do you decide on the city limits? According to the World Urbanization Prospects 2025 report from the United Nations Department of Economic and Social Affairs, the most populous city in the world is Jakarta, Indonesia. Their process involves dividing the area into square kilometers,and estimating population density in each square. Here’s their graphic showing the top 10 cities in the world by population in 2000, 2025, and projected for 2050. It’s interesting to note that Tokyo, the world’s largest city by population in 2000, has grown in population only modestly since then, and isn’t projected to grow further by 2050. However, Jakarta, Dhaka, Shanghai, Karachi,Cairo, and a few others are taking off. I find it hard, with my 20th-century brain, to imagine what it means to have “city” of more than 50 million…