3.5 Statistical: Census

Census Geographies are a special type of statistical geography designed to be used with the UK census of population

In the UK there is a census of population once every 10 years. In recent years this has been for 1971, 1981, 1991 and 2001. The next census will be in 2011. In each census year a different set of census geographies has been designed to permit the collection and dissemination of census statistics.

The geographies of the census tend to be hierarchical in nature. Although census statistics are gathered at one level of geography, the same statistics can be output at multiple different levels of geography depending on the type of research question that needs to asked. This is all possible because the output geographies are designed so that the lowest levels of census output geography nest within the upper levels of census geography. You can see how this works in practice in the following interactive element:

Interactivity 3: Census Heirarchy1_2

1971 Census Geography

- Collection geography: Enumeration District - Output geography hierarchy: Enumeration District; Ward; District; County

1981 Census Geography

  • Collection geography: Enumeration District
  • Output geography hierarchy: Enumeration District; Ward (postcode sector in scotland); District; County / Region
1981 Census Enumeration Districts.

Image 7: 1981 Census Enumeration Districts.

1991 Census Geography

geographies tend to be hierarchical eg : LO2 Census Hierarchy (demonstrates how to read census codes)

  • Collection geography: Enumeration District
  • Output geography hierarchy: England and Wales: ED; Ward; District; County. Scotland: OA; pseudo postcode sector; District; Region
1991 Census Enumeration Districts.

Image 8: 1991 Census Enumeration Districts.

2001 Census Geography

  • Description of collection geography: Enumeration District
  • Description of output geography hierarchy: OA; Ward; District; County/UA. CAS / ST Geographies.
2001 Census Output Areas

Image 9: 2001 Census Output Areas

Since in each census year there is an output geography hierarchy what this means is that you can take the same area based statistics and explore the variance in the data at different levels. Most census statistics are made available at each of these different levels within the overall census geography hierarchy. For example if we were dealing with census 2001 data and our area on interest was total population in Nottingham we could explore the variance in population by the highest level of detail – census output area, up to Ward, up to District and then up to the top level County / Unitary Authority level. You can see this in the image below. Here we have a series of 4 maps that show the same statistics at different levels of geography.

Something you will have noticed between each of the census geographies that we list for 1971, 1981, 1991 and 2001 is that there are differences between each. You`ll remember that when we discussed electoral boundaries we mentioned that the definition of electoral regions needs to be revised frequently to ensure that the democratic process remains representative and that the boundaries reflect changes to the underlying population. The same need to relect changes to the underlying population is true of census geographies. This means that the set of regions used in one year of the census are generally not comparable with a set of regions used in a different year of the census. We can see this to be true if you compare each of the 3 maps above. In each case you`ll notice that the boundaries in each year follow the river that flows through the middle of the region but the actual shape, size and density of the areas varies considerably between each census year. When using census data you need to be aware of the fact that geographies are subject to change between different census years.