“If the world’s 6.9 billion people lived in one city, how large would that city be if it were as dense as…”
When I first saw this map, I was slightly peeved that London appeared to have lower density than San Francisco, or Paris. I lived in London for ten years, and have been in SF for a few months. I hope residents of the latter won’t be too offended if I say that, all too often, even relatively central neighbourhoods feel more than a little suburban.
I decided to go and have a deeper look at the figures. Firstly, at the original post, Tim De Chant (who designed the maps), writes that they’re based on
Strictly city limits. So the San Francisco map, for example, only uses density data for the city of San Francisco and does not factor in Oakland, San Jose, etc.
Now, San Francisco is a city of 600 km², with a population of roughly 800,000. It’s embedded in a larger “combined statistical area” - including the aforementioned cities - of nearly 8 million. The densities for the two? 6,688.4/km² and 320/km² respectively. There’s almost a factor of twenty difference there.
By contrast, London’s nearly 8 million fit into an area barely one-fifteenth that of the Bay Area - making the entire city nearly match San Francisco’s density. The central London boroughs - like Islington, where I lived for six years - come top of the list of districts by population density in the UK, with double the population per square kilometre of SF. (I haven’t bothered to calculate the density of the old LCC boroughs, but my bet would be they handily outrank SF, although I doubt they approach NYC.)
Similarly, the incredible showing by Paris is helped by the fact that the city is still defined by its medieval extent, excluding a large chunk of its metropolitan area: to paraphrase Wikipedia, the city has a population of two million, but the metropolitan area has a population of nearly twelve. The density of the latter is roughly one seventh that of the former - and lower than that of London of SF.
This is, perhaps, too much effort to put into a single graphic, especially one that does such a good job of showing how sprawling a car-centric US city can become (hello, Houston). However, it’s an interesting exercise in noting that defining a city is harder than it may appear.