Thursday, 3 February 2011

A bit of context

The UK police have launched a new website this week, which allows you to look up crime statistics at street level. The figures have been available for neighbourhoods for a while but this level of detail is new and now that the site is back up again, good fun to play with.

The methodology and lack of data history have been criticised. As always with a database this big, looking at the outliers doesn't find you interesting facts (much to the newspapers' annoyance) it finds you anomalies in the data. In this case, the 'most dangerous places in Britain' are streets where the postcode is used as a quick location to log all of the crime that happens in a city centre. It's not that 500 people a month are arrested on the same small street for being drunk and disorderly, just that the police need a postcode for their database, so they use that one.

I've recently moved house, up to my exciting new econometrics job in Leeds, so looked up my new neighbourhood.

Wow. It seemed like such a nice, friendly, quiet little town! Now I can see that just in the last month there have been assaults, burglary, theft from cars... I'm scared.

What about my old address in SE London? I lived there for five years and never had a problem (except for a chav nicking my satnav, but I'm an idiot for leaving it on display in the car.)

Suddenly I feel safer in my new home!

I'm sure a policeman would have looked at the Mirfield statistics and pictured a fairly safe little town. I'm not an expert though and any number above zero looks like a crime hotspot.

If you're producing a dashboard for a non-expert audience - whether it's showing crime or click through rates - then context is essential. Is the number you're looking at good? Bad? Indifferent? The old neighbourhood level mapping did give context and in that very important way was the superior tool.

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