When determining what is the largest city in the world, there are no completely accurate counts of population. If a city has millions and millions of people, an accurate census that counts every single person does not exist. Therefore, the lists of the largest cities in the world use estimation methods to calculate an estimate of the population.
All the lists of population estimates for the world’s largest cities have one thing in common. They list Tokyo, Japan as the largest city in the world. By some estimates, Tokyo has a population of 33,200,000. On other population lists, Tokyo’s population is listed as 34,100,000. In either case, Tokyo is at the top of the list.
The second largest city in the world varies depending on the list being referenced. In some resources, Mexico City with a population of 22,650,000 is considered the second largest city in the world. Other lists have New York, New York with a population of 17,800,000 as the second largest city. On the lists that have New York as the second largest, the population of Mexico City is stated as 17,400,000 which only puts it in fifth place.
Some lists of the largest populations have Mumbai as either the first or second largest city in the world. Mumbai is considered by many to be the fastest growing city. The most common arrangement of the lists of the largest cities in the world show that Mumbai, New York, and Mexico City are very closely ranked, but all three are usually almost always listed below Tokyo.
Some of the differences among the list depend on the estimates and what area of the city is counted. Some lists are organized using estimates that include the suburbs of the city. Other estimates only count the concentrated urban area of the city. Since some large cities have more concentrated populations while others are sprawling, less-dense cities, this can affect how the cities rank on the list.
Shanghai, China and Delhi, India are often near the top of the list. Sao Paulo, Brazil and Lagos, Nigeria also are among the largest cities in the world. Los Angeles, Seoul, and Buenos Aires are often shown among the top ten largest cities.
Some lists estimate how the list may appear in 2015. The forecasting estimates based on population growth include Tokyo as retaining the top rank, but show Mumbai as securing the rank of the second largest city in the world by 2015.