Sunday 25 January 2015

How many people live in Tokyo?

Back in August 2014 when I was preparing some material for teaching students how to query data in a GIS, I devised a very simple example where they had to select all the countries in the world with a lower population than the Tokyo Metropolitan Area (or Greater Tokyo Area, as it's sometimes called). I did this just as an example but since I found the results quite interesting, I quickly turned it into a map and posted it on Twitter, complete with 'Toyko' typo in the subheading. It was really just a quick example of how to query data in a GIS but it also highlighted the massive population of the Tokyo metropolitan area. You can find the full size, original image here. I was prompted to write this blog because the map was reposted on the Canadian Twitter feed @AsapSCIENCE a few days ago and since then my inbox has been a bit busy.

Now, back to the original question of how many people live in 'Tokyo'. Well, when I say 'Tokyo' in the map, I'm referring to the wider metropolitan area, which in 2014 the United Nations World Urbanization Prospects said has a total population of 37,833,000, far beyond the next largest urban agglomeration, Delhi, at 24,953,000. By way of comparison, using the urban agglomeration population (rather than a city's administrative boundaries), Toronto had 5.9 million, London had 10.2 million and Beijing had 19.5 million. Clearly, these definitions include other urban places that are not Tokyo (e.g. Yokohama) but they are recognized as being part of a fairly coherent metropolitan area. 

So, in the map, I'm using a figure of 'approx 36 million' as I say but in reality the UN figure is a bit higher. If we want to narrow the definition down to just the inner urban area then obviously the figure reduces significantly. I'm not usually one to cite Wikipedia, but in this case it's a good place to go to learn about the various definitions of the Greater Tokyo Area/Kantō region. If you don't want to click, here's a summary of some Tokyo populations...
  • Former city area (23 'special wards') - 8.95 million people
  • Tokyo Metropolis - 13.05 million
  • Tokyo Metropolitan Employment Area - 31.70 million
  • National Capital Region - 43.47 million
If we take the metropolitan definition used by the United Nations, then Tokyo does indeed have more people than Canada, at 35.5 million (2014 Statistics Canada estimate) and far more than Australia at 23.7 million (see their population clock). The Tokyo metropolitan population is roughly the same as the whole of California, which currently stands at about 38 million.

Link to chart

This was all just a little bit of map trivia and whilst it seems to have annoyed some people who live in a red country, the point was just to demonstrate the simple analytical power of GIS in addition to the size of Tokyo (to make it more interesting). The data I used are from Natural Earth if you want to have a look yourself and the software I used is a free GIS called QGIS, which is really good. Some other random facts about what happened to my original tweet...

Tokyo metropolitan area

Saturday 17 January 2015

Interpreting political maps

I recently tweeted a couple of maps showing the 100 most and least deprived constituencies in England. I used the 2010 English Indices of Deprivation to calculate this, aggregating the data from smaller areas to parliamentary constituencies. The method is not perfect but on the whole the areas identified are either among the poorest or richest in England. There are 533 constituencies in England so the figure of 100 is roughly the 20% most and least deprived (18.76% to be more precise). I shaded the maps using red for Labour, blue for Conservative, Yellow for Liberal Democrats and so on. The most obvious thing about the maps is, of course, the fact that the most deprived map shows nearly all Labour constituencies and the least deprived shows almost all Conservative constituencies. Click the caption below the images to see interactive versions.

100 most deprived constituencies

100 least deprived constituencies

These kinds of maps often make a big impact and are shared widely but people tend to draw conclusions from the patterns they see that are not necessarily correct - and often conclusion which mirror pre-existing biases and perspectives. For example, some people see these maps and claim that voting Labour makes you poor or that only rich people vote Conservative. Some would even claim that this proves that Labour has failed the constituencies they serve. Opponents would argue that coalition cuts have merely deepened spatial inequalities and hit Labour-voting areas hardest. This is all a bit dramatic, but you don't have to search online long to find such views.

Other people might say that if you want to be richer you should vote Conservative. Other people would tell you not to be so simplistic and point to the way in which voting patterns are formed at the local level. Still others might point to the longstanding economic differences between north and south in England and say that this has something to do with it. Perhaps others will say that the Conservatives are the party of the rich and that Labour are the party for the poor. There are varying degrees of truth in all these views but the point I want to make here is that none of this can be proven just by looking at a political map.

For me, such maps are a starting point for a conversation about what these patterns might mean, whether they are a problem and what might be done about it, if anything. I'm not making these maps because I'm pro-Labour or pro-Conservative or because I think that they prove anything in particular but because I want to draw attention to the patterns and what they might mean. Finally, some observations from the maps...

  • There are no Labour constituencies amongst the 100 least deprived in England.
  • There are 2 Conservative constituencies amongst the 100 most deprived in England.
  • Sheffield Hallam (Liberal Democrat, Nick Clegg) is amongst the 100 least deprived constituencies in England. 
  • There are 5 Liberal Democrat constituencies amongst the 100 most deprived in England.
  • There are 7 Liberal Democrat constituencies amongst the 100 least deprived in England.

It will be very interesting to see how these patterns change (if at all) after the General Election this year.

Wednesday 14 January 2015

Visualising Residential Mobility in Urban England

Last year I produced a few commuting maps of England and Wales after the 2011 Census data were released. Now I've turned my attention to mapping patterns of residential mobility in urban areas of England as part of my work on understanding housing markets. This post highlights some of the patterns uncovered in the data - which are output area level migration flows for England and Wales (about 4 million individual flows). If you're interested in how I did this you can find out in a previous post. The first image is of the urban North West of England and for subsequent images I've zoomed to different parts of the country. I've kept it simple and only showed the flow lines, apart from in the North West where I've also added some place labels. It's all a bit experimental at this stage.

You can find a higher resolution image here

The North East of England

West, East and South Yorkshire

I think some places are missing (working on it)

I've adjusted the brightness a little to make this clearer

What does all this show? It shows what many people may already know or expect but basically it illustrates the extent of residential mobility patterns in some of England's major urban areas - plus a bit more in the South West example above. There's a lot more that could be said about this but for now I'll leave it at that. I'm sorry if your town or city isn't on the map! Maybe next time...

Notes: I've filtered the data so in certain cases some places are not shown (e.g. in the North West image places in North Wales are not visible). Also, I've only shown flows of a certain volume in order to filter out the noise.