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Census Geography: Scotland 1991

For the 1991 census in Scotland, the lowest level "Output Areas" (OAs) were created by the General Register Office Scotland as aggregations of postcodes which had been previously digitized. The 38,254 OAs were mostly created by subdividing 1981 "Enumeration Districts" (EDs) which had themselves been constructed from the aggregation of OAs, allowing a high degree of geographical comparability between census results. Where neat subdivision of EDs was possible, this is reflected in the 1991 OA code, so that ED 12 may have been split into OAs 12A, 12B and 12C. The 1991 OAs contain an average of 125 persons and 53 households, making them smaller than the equivalent 1991 EDs in England and Wales. The minimum threshold for publication of census data was 50 persons and 25 households and no OAs were created to be smaller than this. 156 OAs were large communal addresses to which grid references were assigned but for which no boundaries were created.

OAs nest within postcode sectors, which are the equivalent of the ward level in England. Scottish OAs are groups of unit postcodes that fit as well as possible to higher-level geographical areas. Postcode sectors vary widely in population size. They are variously described by a code which most closely matches their position in the postcode hierarchy (e.g. "EH8 9") or by a code within the census hierarchy (e.g. "6229BL"). There are also electoral wards in Scotland but these do not nest exactly within the census geography hierarchy. 56 Districts are nested within 12 Regions. The codes for these different levels are combined to create a 10-character alphanumeric code. Area names are applied to all levels above the OA. The census geography coding scheme will be found within postcode directories and census datasets relating to the 1991 census.

Digital boundary data are available for all units in the hierarchy but registration is required.


1991 Census geography hierarchy within Scotland

Areatype Code Full code Area name Number Mean population
Region 62 62 Lothian 12 397,554
District 29 6229 Edinburgh City 56 85,190
Postcode sector BL 6229BL EH8 9 1,003 4,756
Output area 12B 6229BL12B (Not named) 38,254 125

Further Readings

Exeter, D. J., Boyle, P., Feng, Z., Flowerdew, R. and Schierloh, N. (2005) The creation of'Consistent Areas Through Time' (CATTs) in Scotland, 1981-2001 Population Trends 119, 28-36