Answer to Map #81

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Answer: This week’s map was a choropleth depicting the average distance that residents of each U.K. postcode area commute to work.

Since this map turned out to be quite difficult, some discussion of the cartographic process may be warranted. Three of the four previous maps had been about the U.S., so I wanted to focus on another country. Somebody suggested that it would be nice to have a map of the U.K., so I went to the English/Welsh census and started poking around. When I saw that the census had collected statistics on commuting, I thought that might make an interesting map. I assumed that there would be target patterns around the most populous cities—that is, as you move farther from the center of the city, people commute longer distances, up until the point where it’s too far to commute on a regular basis and the pattern stops.

The reason maps are so useful is because they help you to visualize patterns you can’t see in the underlying data. When I finished making the map, it didn’t quite look like what I had expected. The target pattern was definitely there around London and, to a lesser extent, Cardiff. The postcode areas where people commute the least are in the heart of the city: EC (East Central London; 6.5km average commute) and WC (West Central London; 7.8km average commute). You can also clearly see from this map the maximum distance that people who commute into London are willing to live from the city: SN (Swindon; 18.3km) and SP (Salisbury; 18.4km).

But these patterns don’t hold in the north. In fact, northern England is very muddled on this map. Some of the lightest colors are in relatively sparsely populated areas, which is the opposite of the pattern we see around London. Instead of trying to explain what’s going on in northern England, I’ll leave that up to you. This map presents a lot of little mysteries. One question is why people in HX (Halifax; 11.9km) commute such short distances. Another is why people in YO (York; 18.4km) seem to commute so much farther. There is a lot to explore on this map.

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