Monday 16 October 2017

Local House Price Growth in England and Wales, 1995 to 2016

On the BBC website and news today there's a great story about house price growth in England and Wales over the last decade. It uses ward-level house price data to track changes over the past decade. I wasn't aware until relatively recently that the ONS had done a lot of the leg-work with HM Land Registry price paid data and aggregated it all to smaller geographies. They publish it down to MSOA level as 'house price statistics for small areas', and very nice it is too. There's median price, lower quartile and a range of other indicators. Naturally, I wanted to see what this looked like, but I thought it would have to be simplified. What I did was take two market price points - £200k and £500k (as very rough approximations for national and London averages) and map the spread of house price growth since 1995. Here's what it looks like in a 30 second animated gif. The geography is the MSOA, with an average population of about 5,400.

Watch this on loop for best effect

I wonder if I should post all the individual frames of this below? Okay, go on then. And you should be able to click to open then in a larger size in a new tab/window. It's interesting that after 2008 there appears to be a geographical contraction and also a bit more volatility and less uniformity of spread - and by 2016 you see a big chunk of the London area in dark red (over £500k average).

Okay, so we can really tell that by 2016 in most MSOAs across England and Wales house prices are at £200k or above and in a good chunk of London and the South (and a few areas elsewhere, notably Cornwall and south Manchester) they are £500k or more. That's all for now. I'll leave you with the same gif as above, but this time at 1 second per frame, plus another earlier version with the year label in the top right.

Slightly different design, same data

Thursday 5 October 2017

Measuring Land for Mountain Goats

Land is frequently contested and fought over. In fact, in the history of civilisation, you could say that land has been at the centre of some quite important disputes (if you really wanted to understate things, that is). Because I'm a) a bit of a nerd and b) technically some kind of planner or geographer, I decided to look into the question of how you measure it. More specifically, I looked at the question of how you measure land area in areas where land is not flat - as it mostly is not across the surface of the earth. I did this one Friday afternoon many months ago with colleagues Ed Ferrari and Ruth Hamilton, and then I wrote up the slide set below. I'm hoping someone out there finds this interesting and/or useful.

The basic problem: land is very rarely totally flat. A 50m x 50m square on a flat plane will cover an area of 2,500 sq metres. But that doesn't take into account slopes, bumps and so on. So when one of your friends asks you 'if you flattened Switzerland, how big would it really be?' - after reading this you should be able to tell them.

To find out more, click to follow the slides below. The slides explain things in more detail and also say a bit about how to do these calculations in a GIS.

If you're too busy to do this, just know that when you take into account the topography of the land, Switzerland would grow by about 7% and Liechtenstein would grow by about 8%. But of course this partly depends upon the resolution of the data you measure it with. These figures come courtesy of Ed Ferrari.

A picture of a mountain goat I found on the internet

To make it easy for you to remember, should you ever want to use these slides, will take you straight there. That's just followed by measure sloping land as one word, after the forward slash.

Notes: spot an error in all this? Let me know. Got better examples? Please get in touch. I believe land is measured most often as if it were on a flat plane. Mostly this probably doesn't matter but I did want to find out what impact there would be if you took slopes into account. There are quite a few notes and disclaimers in the slides, so take a look at those for more information. Mountain goat picture is from this blog.