The Shapes of Cities

For a long time, I've been interested in the shape of cities and I suspect that if you're reading this you might be similarly afflicted. By 'shape' I mean their political boundaries as opposed to their general urban footprint. The latter can be seen by driving around or from a plane window, particularly when it's dark, but the political boundaries are much less obvious. This is particularly true of US cities. Take Houston, Texas - the first example below. 

The boundary of the City of Houston - Google Map

Look closely at this and - at least if you're not used to the political geography of American cities - you might be very confused by this fragmented, segmented mess of boundaries. Then go to Google maps and try different search terms, such as 'city of los angeles' or 'city of columbus' (Ohio) and you'll soon discover that Houston isn't that unusual at all. Try it for other cities and you'll see what I mean. Columbus, Ohio is a particular favourite of mine as I know it quite well having lived there for a couple of years in the early 2000s.

City of Los Angeles - Google Map

City of Columbus (Ohio) - Google Map

These unnatural-looking boundaries are the result of a complex mix of geography, history and politics that have real impacts on the ground. From education and transport to housing and waste management, the shapes of cities really do matter in this respect. Of course, this is a much-studied topic in urban studies, not least by Professor John Parr of the University of Glasgow. In Parr's economic definitions of the city, he outlines four types - but none of these explain the kinds of boundaries we see above. One major explanatory factor in all of this, of course, is tax revenue. But I'm not going to get into that now because it opens up a whole range of other topics, including white flight, suburbanisation, and schooling, amongst other things. The point is that the 'shapes' of cities are not accidental and who is included or excluded is inherently political. 

In the United Kingdom, we might not have such unusual city boundaries, but the political geography of our cities is far from perfect - perhaps one reason for the resurgence of the 'city-region' concept over the past decade or so. When we're talking about urban economies, it makes much more sense to think about the functional urban area than it does to use data associated with an arbitrary political shape. This is as true in the US as it is in the UK. The example below shows that the City of Atlanta has less people than the City of Liverpool and that it's only slightly bigger in scale. But anyone who knows anything about these places will understand that 'Atlanta' is much bigger than 'Liverpool and is vastly more sprawling, with a metropolitan population of around 5.5 million compared to less than a million in 'Liverpool' (by one definition). 

Atlanta vs Liverpool - which is bigger?

These kinds of issues are part of the reason organisations like the Centre for Cities use the Primary Urban Area definition of cities for the 64 largest urban areas of the UK. In a recent study, I used a definition developed by Geolytix which is based on the 'sprawl' of the urban area rather than political boundary and found this to be a much better fit than the administrative area. When conducting comparative analyses of cities, we need to ensure we are comparing like with like, and using a functional definition often helps avoid the kinds of underbounded/overbounded problems that arise when (e.g.) comparing places like Manchester and Leeds. The former is normally said to be 'underbounded' because the functional urban area is much bigger than the local authority area of the same name and the latter is said to be 'overbounded' because of its much wider local authority area, which extends beyond the core urban fabric. For a comparison of UK 'city' sizes, see this graphic I produced a few years ago:

All cities shown at the same scale

Surely there's a point to all of this? 

Yes, glad you asked...

For planners, politicians, residents and neighbours, the shapes of cities matter enormously. It might dictate which school your children can go to, whether your local facilities are well funded, whether you have a well-functioning local transport system, when your bins get emptied, how many pot-holes you have in your street and all sorts of other things. But let's not get into that now. Instead, I'll end with another city shape, this time for the City of Detroit (one of my favourite cities, but much-maligned).

Detroit - 8 mile boundary line to the north

Where is all London's new housing?

Some of my recent work on housing markets, mortgage lending and housing search has led me to consider the question of where, exactly, London's new housing is located. On a recent visit to King's Cross I was amazed by the sheer scale of development, particularly all the new flats. Because I've been working with the data for another project - and recently re-examined it for a project proposal which explicitly didn't focus on London - I thought it would be interesting to see whether my perception of the flats boom is based in reality. Of course it is! 

The maps below are based on all new build homes sold in London from 1 June 2010 to the end of April 2015 (the most recent data). During this time, according to HM Land Registry 'price paid' data, there were 42,938 transactions on 42,813 properties. This indicates that quite a few properties are not being picked up in this dataset - e.g. compare it to the completions data from the London Datastore. Nevertheless, the patterns and distribution of property types is revealing. 88.8% of transactions were for flats, 7.1% for terraced houses, 2.4% for semi-detached properties and 1.7% for detached houses.

All property types

Flats

Terraced houses

Semi-detached houses

Detached houses

Clearly, the mix of new housing - and its relative low volume - is something that many people have commented on before, but I've not seen many people look at the geographical distribution in this way. The important questions arising from these maps - as ever - is why are things the way they are? That's something the maps can't tell us but it does provide an interesting starting point for debate. The discrepancy between the Land Registry data and data on completions is also not surprising owing to the way new build housing is sometimes sold, but it would be interesting to explore this more in future. If you do happen to have a few million quid to spare, good luck finding a new detached London house to live in!

A note on the maps... I've geocoded the price paid data using Ordnance Survey's Code-Point Open dataset, which can match sales to postcode units, rather than street addresses. The transparent bubble map is of course far from perfect but I've used it here to convey the scale and location of new housing, rather than to offer a precise fix. So long as it gives the impression of there being a massive splodge of newbuild flats in Central London that'll do for now. I am aiming to highlight the general scale and geography of development as a fairly quick experiment to see what might be done with the data. No plans to make it interactive (update: the best laid plans of... see map point datadump below).



Update (1715, 22 June 2015): I fixed the glitches, which were caused by a rogue space here and there in the codepoint open file. Moral of the story? Build more houses (I think). Always a giveaway when there aren't many dots in Wandsworth. The numbers were correct all along though. Finally, I've added in some information from HM Land Registry on properties not included in the price paid data.

Data excluded from Price Paid dataset - link

How Many People Live in Inverness?

Coming back to a familiar topic here - that of the population of places. It is interesting in its own right - see this site for information on everywhere, but it is also pretty important in terms of policy formulation, implementation and delivery. Examples include Manchester's missing 25,000, (which equates to £7.5m in funding) and Slough's undercount of new migrants from outside the UK (which also has relevance for the Inverness case). Inverness is where I'm from and it's grown pretty quickly in terms of population over the past 20 years in particular, but there's some doubt as to exactly how many people live there. Everyone has ideas about this - from more generous figures (giving a 'city-region' population of 66,000 in 2001) to figures for the 'city' itself - a rather more conservative 40,949. This just illustrates the inherent difficulties in defining the population of places that have no statutory boundaries. Even if that was the case, the difference between city populations and urban area populations is often very large, as in the case of Manchester (the district) and the Manchester city-region.

So, I've done a bit of analysis, as follows. I attached the data zones for the Inverness city area (core city plus Smithton, Balloch, Culloden and other bits here and there) to the data zones for which we have mid-year 2006 population estimates and come up with a population of 54,685. I make no claims that this is a definitive representation of the population if Inverness but it does give an idea of how many people live in the area shown in the image below showing the google map of the population of Inverness that I've created. [The map may take a moment to load over a slower connection and I may eventually move it off the server it's on right now so the link may eventually die, but the screenshot below is good forever.]

So, once and for all the question has been answered. Or has it?

Everything is Connected

One of the things I said I'd be blogging about is urban issues and things to do with urban life, specifically as they relate to planning. However, I thought it would be good to do a quick post on the topic of connections and how it's really impossible to fully separate the urban from the non-urban or rural. This is a topic which a colleague of mine, Andreas Schulze Bäing explored in his PhD thesis and one which I do research on, but without so much focus on the rural dimensions. I'm also aware that I come from an area that is not exactly an exemplar urban area (the Highlands of Scotland), even though I've lived all my adult life in cities (Glasgow, Columbus (Ohio), Liverpool). So, if you're from a rural area like this...

... it doesn't mean that cities are irrelevant. In fact, given that they are now seen as the drivers of economic growth in many advanced industrial economies, we really should be aware of how things are connected. When you look at the major migration patterns in the UK, these kinds of connections are more obvious.


When you look at the patterns in even more detail, in this 3D image I created for migration patterns in the North West of England (high in-migration areas in red, out-migration areas in blue), we start to get a better understanding of the ways in which cities import people (mainly students and young people). However, they do export families who generally tend to rely on urban areas for a living but don't want to live there... But that's another matter.



So, everything is connected to everything else. This is exactly what Waldo Tobler's First Law of Geography states and I am a firm believer in it. Nothing should be studied in isolation (especially in planning) and that's why much of my work includes a spatially dynamic element. The relative importance of this connectivity may vary, but it is invariably important. We need to see the big picture if we are to understand what's going on in our own back yard, so to speak.