Page last updated: 6-NOV-2007

Deprivation

Geographical units

There are three main choices of geographical unit for small area analysis (in descending order of average population size):

  • Postcode sectors: There are 1,010 postcode sectors in Scotland, identified by a combination of the first five characters of the postcode (representing 937 areas) and the Council Area. The average population is 5,012, but they vary  considerably in size. The smallest postcode sector represents just 51 people and the largest 20,512.

  • Data Zones:  These are designed to represent neighbourhoods and have an average population of around 700 people.  There are 6,505 data zones, and they are comparatively homogenous in size with an average population size of 778. The smallest data zone represents 476 people and the largest 2,813 people.

  • Output areas: These are the smallest geographical unit for which Census data are available  There were 42,604 output areas at the 2001 Census with a mean population size of 119 people. The smallest output area represents 50 people and the largest represents 2,357 people. This wide variation is due to a few large output areas with populations in communal establishments.

Pockets of deprivation are best identified using as small geographical units as possible, so other things being equal, the use of output areas should be the favoured choice.  However, the 1981 and 1991 Carstairs indices are only available for postcode sectors.  The 2001 Carstairs indices are available for postcode sector, data zone and output areas. The SIMD is available for data zones.

 

Deprivation Categorisation

There are four main categories:

  • 7 Categories have previously been used in ISD to split the population.   The categories are of unequal size and the most and least deprived groups include the smallest populations. For statistical analysis it is desirable to have equally-sized groups so ISD have now moved away from this categorisation.

  • Deciles used within ISD divide the population into ten equal categories so that 10% of the population falls into each decile (population weighted). Deciles have been calculated at Scotland level and also within individual health boards. Decile 1 is the least deprived, decile 10 the most deprived.

  • Quintiles used within ISD divide the population into five equal categories so that 20% of the population falls into each quintile (population weighted). Quintiles have been calculated at Scotland level and also within individual health boards. Quintile 1 is the least deprived, quintile 5 the most deprived.

  • Top and bottom 15% relate to National targets being set by the Scottish Government Health Department which will be based on the 15% most deprived and 15% least deprived people in Scotland.


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