Tuesday, 31 January 2012

Population Density in New York City

In some recent posts I've been looking at the issue of population density. I did this for London in December and for the continental United States earlier this month. Given the extremely high population density in Manhattan, I thought it would make sense to take a closer look at New York City. So, I took some publicly available NYC GIS data, some 2010 US Census data and went to work. The result is the 3D map image below...

The mapping here is done at the Census Tract level, of which there are about 2,100. These areas have an average population of about 4,000 though there is some considerable variation between areas in that several tracts contain more than 10,000. The spatial patterns above are fairly obvious and, as expected, Manhattan dominates once again. However, the individual Census Tract with the highest population density is actually in Corona, Queens with a figure of 216,000 persons per square mile*.

There's a lot more information on New York City's 2010 Census results on these pages, from the New York City Department of City Planning...

* N.B. It's important to point out here that these areas are much less than a square mile, but I'm using square miles since it is a conventional measure of population density in urban areas).

Tuesday, 24 January 2012

Cities Outlook 2012

Yesterday saw the publication of the Centre for Cities annual 'Cities Outlook'. The lovely people at CfC have now produced this publication for five years and it receives significant press attention (and was even one of the most read on the BBC website). I've written a thing or two about cities on this blog so it thought I'd just provide a few notes on this most recent incarnation of Cities Outlook...

  • The first thing to note is that Cities Outlook 2012 uses Primary Urban Areas as a proxy for cities. See this document (and p.106-109 in particular). PUAs are not just the local authority area but rather a grouping of local authorities around a core local authority area. PUAs only exist for England (and there are 56 of them). For Scotland, Wales and Northern Ireland the definitions of 'city' are slightly different - see p.25 of Cities Outlook for more on this. 
  • This has been covered a lot elsewhere, but 'the recovery' is at present not looking very good when compared to previous periods of economic turmoil - the chart on p.7 is particularly illustrative of this point.
  • There is no harm in reinforcing key messages, and Cities Outlook does this many times. The most important of which is probably: "Unemployment is likely to become an increasing problem in 2012". When the youth figures are taken into consideration (1m+) we can only speculate at how this will play out in the long term.
  • Hull and Cambridge are not necessarily on the same trajectory! See p.15 for more on this. Of course this is not really a fair comparison in some ways but it does illustrate some of the important differences between cities.
  • On p.31, I'm not convinced of the utility of the landmass comparison for the entire UK, particularly when the definitions vary across the UK (even if the graphic is quite pretty).
  • Let's all move to Milton Keynes (p. 36). On second thoughts, maybe not.
  • Three cheers for Aberdeen: "Every city in the UK apart from Aberdeen saw a decrease in their business stocks from 2009 to 2010". More information on business type would be useful here of course. 
  • Some useful emissions data on p.65, which I suspect isn't entirely fair on Middlesbrough without some additional contextual information...
  • A very interesting piece of work!

Sunday, 15 January 2012

England's Green Belt - 'Closed' Data

At the moment I'm doing some work related to housing market search behaviour and I have a very interesting dataset for it. I thought it would be nice to compare housing market search patterns to where areas of green belt land in England are. This is where I ran into problems. Everyone knows that there is green belt land in England, but knowing precisely where it is and how to get this in digital format is more difficult.

It seems that, for whatever reason, Landmark Information Group have the rights to the data, as you can also see from this BBC map. The problem is, I was quoted a price of £35,000 + VAT for the full dataset. I've nothing against Landmark but I couldn't figure out why it would be so costly or why it is not open data. To cut a long story short, I got the data directly from the Department for Communities and Local Government but the licence means I can't really do much with it publicly, so I've made a small map below showing what it looks like.

The problem with this is that if a normal person* just wants to check which areas of the country are green belt and which aren't (and given current proposals to reform the planning system in England, this is quite important!), it cannot be done easily, if at all. What I'd really like to do is take the green belt shape file and put it on top of a Google map and then let the world see it. But it's not my data, it's not open data, so I can't. This seems like a pity and not just because I'm addicted to mapping things. It seems like a pity because this information should, I feel, be in the public domain in an accessible format. 

*Clearly, I'm not a normal person or I would be doing something else at this time of day/week.

Monday, 9 January 2012

Daytime Population in the United States

My last post on London's Daytime Population is getting a lot of page views, which is nice, so I thought I'd do something else on the same topic. Although I do try to make nice images with data, there are some very important planning-related issues here. The first is just to do with the importance of knowing how many people live in an area. In New York City, the city challenged the 2010 results because it could have led to less federal aid, and in the UK in 2011 the city of Cardiff claims there was an undercount which could have led to them missing out on £85 million of funding since 2001. In relation to daytime population, this is also very important, but more difficult to calculate, as Robert C. Schmitt discussed in 1956. So, I looked at the 3,111 counties of the lower 48 states in the US and mapped them by daytime population density, as you can see below.

Why does it matter that we know what the daytime population of a place is? Well, there are many reasons including planning for public transit, traffic flow, infrastructure needs, utilities and even for developing evacuation procedures (Schmitt was writing in 1956 but perhaps this last point is still relevant today).

In the United States, the county with the highest daytime population density is New York County (aka Manhattan). It is far and away the leader in this category, with 126,100 persons per square mile. That doesn't quite match the daytime population density of the City of London but bear in mind that Manhattan covers 22 square miles! Manhattan's daytime population is also about 1.3 million more than its total resident population, which in 2010 was about 1.6 million.