How do you calculate the percentile ranking of a postcode?

There are many more postcodes, 1.7 million than there are typically crimes and ASB incidents in a given month, around 400,000 in England, Wales and Northern Ireland – and of course they are not all evenly distributed and the locations are not always so precise to protect the anonymity of victims and ongoing legal proceedings. So to get some close approximate idea, you have to widen the catchment area and increase the time capture. We have done this by matching postcodes to within Lower Layer Super Output Areas (LSOA) – 34,751 in England and Wales plus those 890 Super output areas in Northern Ireland (NISOA) – and cover the previous 24 months, not including the area in which it is located in order to create a 0 and a 100 ranking.

Basically, the rankings are generated by comparing the crime rate of a given LSOA or NISOA to the crime rate of all the other LSOAs and NISOAs.

Here is an example for the postcode SW1Y 5ED. To make it easy to understand, we use a number that gives a rank and a score, so 100 equals the most crime within that area compared to the rest of the country and 0 equals the lowest. Notice the quite dramatic difference when you adjust for daytime population – a unique feature of UKCrimeStats.

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