So, there’s a map that’s been doing the rounds on city nerd social media, that’s annoying the hell out of me.

In an attempt to illustrate quite how big London is by mapping other British cities onto its boroughs. And while it’s not wrong, exactly, it is certainly misleading.

Here it is:

 

 

Looking at this, the first thought that flits through your mind is, “Wow, London is huge!” It contains the population of no fewer than 19 other British cities – and not small ones, either, but the regional giants like Glasgow, Birmingham and Leeds.

The problem is that, as big as the capital is, it isn’t big enough as that map implies: not really, not if you draw the lines in any sensible way.

To explain why, look at “Manchester”. That map suggests it has the same population as just two London boroughs: Hackney and Haringey. Each of those has a population of 260,000, give or take; the City of Manchester, as of 2013, had a population of 515,000. So, yes, they match up.

Except – the City of Manchester isn’t the whole of Manchester, is it? Not in any sensible world. It’s just one of the 10 boroughs that make up Greater Manchester, and not even the only one that contains important Mancunian things. Manchester United has its grounds in the borough of Trafford. A chunk of the central business district is just over the Irwell in Salford.

These places, on any sensible definition, are a part of Manchester: include them, as this map doesn’t, and you end up with a population of around 2.7m. That’s still less than a third that of London (which passed 8.6m last year). But it’s much bigger than the map above implies.

It’s the same pattern with several of the other cities here. The city of Liverpool has a population of around 470,000, on a par with one and a bit London boroughs (Barnet is a biggun); but the entire urban area is around 875,000, so nearly twice that. Barnet is big; it isn’t that big.

Birmingham here looks huge, covering five different London boroughs. But the 1.1m it contains is still way less than the 2.5m that live in the entire urban area.

So, we’ve drawn up our own version of this map. Here it is:

A note on the figures. There’s no way of comparing the populations of different cities that is entirely and obvious fair: any attempt at drawing a line around a British city will cause arguments from those who’d rather be in or out.

But we’ve done our best by using a single data set – that of urban area populations calculated by Demographia*, published last year, which we wrote about here. That means that Brimingham includes Wolverhampton, and Leeds includes Bradford, among other things. But since London includes, say, Croydon, which would be a fair size regional city in itself, that didn’t seem unfair.

Those caveats made, what we found is that, on a fairer comparison, London doesn’t include anything like 19 other British cities. It’s big, sure, but only big enough to contain four other urban areas – the next three biggest (Manchester, Birmingham and Leeds) and Liverpool, which ranks about 7th**.

That’s plenty big enough, surely? London is clearly and self-evidently huge. Do we really need to fiddle the figures to make it look even bigger?

*On their definition, of course, London is a bit bigger than these 32 boroughs but it was the best we could do.

**Glasgow is bigger, and so, if you count it as a single entity, is the Southampton/Portsmouth/South Hampshire urban area; but if we included those, the numbers didn’t add up, so we jumped to Liverpool.