Every year or so, Demographia, the St. Louis-based consultancy, publishes the World Urban Areas Report – a sort of bumper book of city population stats.
The report is a veritable treasure trove of demographic stats for city nerds. If you want to know whether, say, Edinburgh is one of the 1,000 biggest cities in the world, then Demographia will tell you. (It's not, it's just outside at joint 1017th). And if you want to know whether Paris covers a bigger land area than London, it'll tell you that, too. (It does: 2,845km2, as opposed to 1,738 km2.)
It even includes estimates for the size and density of hundreds of towns so tiny that you're slightly surprised to find that anyone on the other side of the Atlantic has even noticed they exist. (Favourite example: Kidderminster*.)
But the most fun is to be found in the first half of the report. Table 1 includes the 1,022 built-up areas in the world that house 500,000 people or more, ranked in order of population; Table 2 ranks the same cities in order of land area.
I don’t know about you guys, but we are stoked.
(*55,000 people in 16 km2, giving a population density of 3,400 per km2, since you ask.)
Understanding the numbers
Explanations first. The report defines urban areas as
...a continuously built up land mass of urban development that is within a labour market (metropolitan area or metropolitan region)... [and] contains no rural land.
We should probably also note the reports caveat, about the limits of its own methodology:
Revisions are made as more accurate satellite photographs and population estimates become available. As a result, Demographia World Urban Areas is not intended for trend analysis.
Year-to-year changes indicated in population and land area may merely reflect better data that was not used before and may not, therefore indicate a trend.
In other words, if this year's report has a larger estimate for a city's population than last year's report, that might mean the city has grown. Then again, it might just mean that new, more accurate data has appeared.
Moreover, nearly all of the data is estimated. Appropriate caution is therefore advised.
The biggest cities, by counting people
Anyway, let’s get to the fun bit. Here are the 10 largest cities in the world by population:
It’s pretty familiar stuff. The top 10 is dominated by Asian cities, with a strong showing from New York City. Tokyo is far in the lead, with Jakarta and Delhi coming up behind. For anyone who pays any attention to this stuff, there aren't at first glance any massive surprises.
We're not supposed to compare with last year's figures for all the reasons laid out above, but what the hell, here's the 2015 top 10:
There are two big differences worth noting. One is that only one Chinese city is now in the top 10, down from three last year. (Beijing and Guangzhou are now ranked 11th and 13th.) All three have seen their populations revised downwards: this seems to the result of previous over-estimates, rather than mass evacuations.
The other noteworthy trend is the sudden appearance in the top 10 of Mumbai, with nearly 23m people. Last year, it ranked 13th with 17.7m. In a section headed "Revised data: highlights", the report notes:
The Mumbai built-up urban area has been expanded to incorporate the Bhiwandi, Kalyan and Vasai-Virar urban areas.
In other words, it isn't that a population the size of Madrid has moved to Mumbai over the last year. Rather, it's become clearer that the megacity has expanded to swallow surrounding areas.
You can see why ranking cities is a complicated business.
The biggest cities, by measuring land
As noted, most of the biggest cities in the world by population are in Asia. Most of the biggest cities in the world by physical size are, well, somewhere else.
Suddenly, with the single exception of Tokyo, Asia doesn’t even feature. Eight out of 10 are in the US. Atlanta has an estimated 5.1m residents, so measured by population it’s the 79th largest city in the world. Measured by land area, though, it ranks fourth.
I guess this is what happens when you build your cities around the car.
Incidentally, the report estimates Atlanta's population density to be 700 people per km2. The comparable figure for Dhaka in Bangladesh – 16.2m people, the 16th largest city in the world - is 44,100.
Dhaka is 63 times more crowded than Atlanta.
All the megacities
One more chart: this is the top 36 by population.
The reason we've stopped at that arbitrary point is not to get London into the rankings (well, not only for that reason). It's because the common definition of megacity is that with a population over 10m.
This is all of them. We've colour coded them by continent:
That's three each in North America, South America, Europe and Africa.
But the remaining 24 – two thirds of all the world's megacities – are in Asia. Five of them are in China alone.
Here, because we love you, is the data used in that graph. Enjoy.
|9||New York City||20,685,000|
|26||Rio de Janeiro||11,815,000|
|35||Ho Chi Minh City||10,075,000|
And if you want more of this stuff, here’s our report on the 2015 edition of the Demographia World Urban Areas Atlas.
Jonn Elledge is the editor of CityMetric. He is on Twitter, far too much, as @jonnelledge.