What is a city, anyway?

This, believe it or not, is London. Image by Tom Tired of London

Okay, there's a question we're going to be wrestling with a lot at CityMetric. I'm not saying we're going to answer it any time soon, but the least we can do is ask it, and explain why it constitutes a problem. Here it is:

What, actually, is a city?

At first glance this probably looks like a stupid question, the sort of thing you'd get from a four year old, like "What are unicorns made of?" or “Why is the sky blue?” But (spoilers) it's not.

To explain why, it helps to have a worked example or two. London, official figures tell us, has a population of somewhere around the 8.3 million mark. Paris has a population of roughly 2.3 million. So, one might naturally conclude, London is a lot bigger than Paris.

Except, if you look at a different set of figures, it's very clearly not.  Demographia has been publishing a statistical guide to the World's Urban Areas for a decade or so now. Its latest edition, published in May, has Paris on 11 million – four times larger than the official statistics and well ahead of London's 10.1 million.

Then you look at this dataset from the official statistical agency of the European Union and the figures get even bigger but the order's swapped again. Eurostat has Paris on 11.9 million and London on 13.6 million.

You don't have to be a geographer to guess that these three sets of figures are working from different definitions. You can probably even make an educated stab at what each set of figures represents. They are, respectively, the population of the region governed by the city's own authorities, of the continuous built up area, and of the larger metropolitan region.


But which of these is ‘right’? The answer is, infuriatingly, all of them – or, if you prefer, none of them.

To most people, most of the time, none of this is actually a problem: no one ever failed to understand the concept of London because they were unclear on whether you were counting Watford or not. But there are two contexts in which it matters a great deal.

One is its impact on the workings of city governments. If you're the official charged with coming up with a strategy for meeting an area's housing or transport needs, say, then it would help to have some control over the whole of that city.

Very often, though, you don't, so infrastructure investment is likely to focus on the city proper: not only is official power strongest there, but its population get a vote in local elections. Administrative borders can thus end up warping the fabric of the city itself. Just look at the apparently arbitrary places where the New York Subway terminates.

The other reason why which this definitional confetti matters is that it poses a massive barrier to anyone who actually hopes to analyse the urban landscape. Professor Geoffrey West is a theoretical physicist at the Santa Fe Institute, who in recent years has conducted a number of comparative studies on cities. “You'd think by now all the urban planners would have an operational definition of a city that you just could look up,” he says, with some exasperation. “Well that doesn't exist."

As a result, the moment you start trying to quantify any aspect of city life – or worse, compare two cities – you run into difficulties. How many people live in Mumbai? What's the size of New York's economy? Which is more densely populated, London or Paris? All too often, the answer is ‘it depends’. "It's a problem that's plagued a lot of our research," West adds. "And it reflects how little work has been done to quantitatively, analytically, and scientifically understand cities."

The upshot of all this is that what a city is, and where it ends, is a surprisingly subjective matter, and any attempt to nail it down is likely to throw up anomalies. All you can do is keep track of which definition you're working from, and make sure you never, ever, compare apples with larger urban zones.

Here, for future reference, is a quick guide to the main ways of defining cities, which we’ll be trying very hard not to mix up.

 

The municipality

The political definition of a city. Paris is 20 arrondissements, New York is five boroughs, London is 32-plus- that-awkward-finance-y-bit-in-the-middle.

The advantage of this definition is that it’s nice and straightforward and easy to exert political power over (or find data on, come to that). The disadvantage is that it tends to throw up anomalies: some municipalities exclude large swathes of suburbia; others include sudden patches of countryside. The official definition of London includes North Ockendon, a tiny Essex village outside the M25, but excludes Buckhurst Hill, a contiguous central line suburb well inside it.

 

The urban area

This, one might think, is the contiguous urban sprawl: the thing you can point to on a satellite photograph, or from a plane by night.

Life, though, is rarely so simple. For one thing, areas of development separated by less than 200m of open space will generally be bracketed together as a single urban area, on the grounds that anything you can cross in under two minutes doesn’t count as ‘the country’.

For another, there are features like parkland and forests to contend with, so sometimes you’ll notice a distinction between ‘urban area’ (which includes suburban open spaces) and ‘built up’ area (which doesn’t).

There is also no single universal definition of what counts as an ‘urban area’. Most countries define it as one with at least 400 inhabitants per square kilometre. In the US it’s 1,000 people per square mile, which is nearly identical; in Australia, it’s 200 people per square kilometre, which isn’t.

 

The metropolitan area

A city's effective economic footprint, typically measured by commuting patterns. Satellite towns and ex-urbs may not look like part of a city – but since they wouldn’t exist without it, the thinking goes, they should count.

There are two problems with this idea, however. The smaller one is that you end up counting a lot of people who reject the idea they live in a city at all, if only because they made a conscious decision not to (hello, Surrey).

The bigger problem is that it's largely subjective. What proportion of people need to commute into a city to be part of its travel-to-work area is a matter of judgement. And what if a town between two cities contains large numbers of people who commute to both? Is Warrington a satellite of Manchester, or one of Liverpool? Does Princeton belong to New York or Philly?

The consequence of all this is that different countries use different definitions. While agencies like Eurostat have attempted to harmonise these, there's no current data set that does so worldwide.

Here’s an example of all these various definitions at work. This is Paris, c2008:

That tiny maroon nucleus is the city proper. Surrounding it you have the larger built up area (red), the official urban area (orange) and the metropolitan area (yellow). Suddenly, you can understand why the figures for the city’s population seem to vary by a factor of four. 

 

Just to make things more complicated...

While a metropolitan area will typically contain more than one urban area, the same can be true in reverse. Look down from an aeroplane, and you might think that San Diego and Tijuana are a single city. But there’s a whopping great international border between the two, which most of the area’s population aren’t free to cross. So is it one city, or several? How do you define them? As ever, the answer, awkwardly, is “it depends”.

 

Lastly, some definitions we won’t be using

The bizarre official phenomenon of British city status, an honorific handed out by the queen, which means that Ely (pop: 20,000) and St David’s (pop: 2,000) have the same official status as Manchester. The equally bizarre habit in some parts of the US, of appending the word ‘city’ to any cluster of four broken down sheds and a dog. What of these, eh?

Well, these are silly and we intend to ignore them. So there.

Images: Photo of Pratt's Bottom courtesy of Tom Tired of London, taken from Flickr under a creative commons license; map of Paris adapted from Wikimedia Commons.


 

 
 
 
 

There isn’t a war on the motorist. We should start one

These bloody people. Image: Getty.

When should you use the horn on a car? It’s not, and anyone who has been on a road in the UK in living memory will be surprised to hear this, when you are inconvenienced by traffic flow. Nor is it when you are annoyed that you have been very slightly inconvenienced by another driver refusing to break the law in a manner that is objectively dangerous, but which you perceive to be to your advantage.

According to the Highway Code:

“A horn should only be used when warning someone of any danger due to another vehicle or any other kind of danger.”

Let’s be frank: neither you nor I nor anyone we have ever met has ever heard a horn used in such a manner. Even those of us who live in or near places where horns perpetually ring out due to the entitled sociopathy of most drivers. Especially those of us who live in or near such places.

Several roads I frequently find myself pushing a pram up and down in north London are two way traffic, but allow parking on both sides. This being London that means that, in practice, they’re single track road which cars can enter from both ends.

And this being London that means, in practice, that on multiple occasions every day, men – it is literally always men – glower at each other from behind the steering wheels of needlessly big cars, banging their horns in fury that circumstances have, usually through the fault of neither of them, meant they are facing each other on a de facto single track road and now one of them is going to have to reverse for a metre or so.

This, of course, is an unacceptable surrender as far as the drivers’ ego is concerned, and a stalemate seemingly as protracted as the cold war and certainly nosier usually emerges. Occasionally someone will climb out of their beloved vehicle and shout and their opponent in person, which at least has the advantages of being quieter.

I mentioned all this to a friend recently, who suggested that maybe use of car horns should be formally restricted in certain circumstances.

Ha ha ha. Hah.

The Highway Code goes on to say -

“It is illegal to use a horn on a moving vehicle on a restricted road, a road that has street lights and a 30 mph limit, between the times of 11:30 p.m. and 07:00 a.m.”

Is there any UK legal provision more absolutely and comprehensively ignored by those to whom it applies? It might as well not be there. And you can bet that every single person who flouts it considers themselves law abiding. Rather than the perpetual criminal that they in point of fact are.


In the 25 years since I learned to drive I have used a car horn exactly no times, despite having lived in London for more than 20 of them. This is because I have never had occasion to use it appropriately. Neither has anyone else, of course, they’ve just used it inappropriately. Repeatedly.

So here’s my proposal for massively improving all UK  suburban and urban environments at a stroke: ban horns in all new cars and introduce massive, punitive, crippling, life-destroying fines for people caught using them on their old one.

There has never been a war on motorists, despite the persecution fantasies of the kind of middle aged man who thinks owning a book by Jeremy Clarkson is a substitute for a personality. There should be. Let’s start one. Now.

Phase 2 will be mandatory life sentences for people who don’t understand that a green traffic light doesn’t automatically mean you have right of way just because you’re in a car.

Do write in with your suggestions for Phase 3.