Notes to maps continued
This type of visualisation of religious mix is called "choropleth mapping". Each areal enumeration unit (here, district authority) is filled with a colour, to symbolise a particular data range.
Here, five data ranges are depicted, using the Jenks or "natural breaks" method. This minimises variation within the five ranges, and maximises variation between the five ranges. Therefore district authorities that share a colour are statistically more like each other than units in other colour classes. However, take care when comparing the maps: the five data ranges are not the same across maps.
The data are depicted by ‘district authority’. These tend to be what people mean by ‘local authority’. In some parts of England, the functions of local government are split between the County and district authorities, so that ‘local authority’ is too loose a term. Here we mean local authorities below the county level: district authorities, unitary authorities, metropolitan district authorities, and London boroughs.
Note also that local authority boundaries were reorganised in 2009. The boundaries depicted here are those for 2001.
Religious data source: Office for National Statistics
District authority boundary data source: EDINA UKBORDERS
This work is based on data provided through EDINA UKBORDERS with the support of the ESRC and JISC and uses boundary material which is copyright of the Crown.