1.1 Introduction

The first detailed results of the 2001 Census released during 2003 brought with it a new geography – Census Output Area (COA). For the first time in English census history, data was collected by Enumeration District (ED) geography but released by Census Output Area. EDs are designed for efficient data collection whilst COAs are designed to provide the most enduring statistical geography to date.

COAs are based on groups of similar adjacent unit postcodes aggregated to provide a compact highly homogenous area in terms of housing type and tenure, whilst achieving a minimum population threshold of 100 persons or 40 households. Due to these design thresholds the COAs could only be finalised once the census data had been collated into the relevant databases. A geographic information systems approach was used to iteratively define the census output area boundaries and constrain them to Census Statistical Ward boundaries.

Another first for the 2001 Census was the provision of COA digital boundary files free of charge to the end user. The provision of digital boundaries for COAs with accompanying lookup tables enables the GIS user to produce coterminous boundaries for wards, health & local authority organisations from the same source data. The West Midlands Health GIS service has done this and is able to share these boundaries with those organisations who have signed up to the HMSO Click Use licensing scheme.¹

When considering the use of census data at ward level it should be noted that there are two types of census wards – Census Area Statistics (CAS) wards & Standard Table (ST) wards. There are 761 CAS wards in the West Midlands and 758 ST wards. CAS wards are used to provide the most detailed census counts and uni-variate tables whilst ST wards are used to provide theme tables about subgroups of the population where data for multiple variables are cross-classified. In order to preserve the confidentiality of the small numbers in the cells of multi-variate tables the Office for National Statistics (ONS) must suppress data for those wards with less than 1000 population or 400 households. The data for these suppressed wards is included in adjacent ‘host’ wards. There are three wards in West Midlands affected by this suppression, Clun ward is aggregated with Clun Forest; Keele with Madeley and Chirbury with Worthen ward.

2001 CAS wards and derived Primary Care Trust (PCT) and local authority boundaries are used to report health data in this edition of Key Health Data.

1.2 2004 Electoral Ward Boundary Changes

Since the delivery of the COA boundary data the cycle of electoral ward boundary revisions has continued. In January 2004 new ward boundaries for Birmingham, Coventry, Dudley, Sandwell, Solihull, Walsall and Wolverhampton were defined by statute. The most significant changes are within Birmingham where there is one whole new ward in the north of the city – Sutton Trinity plus significant boundary changes in many other areas across the city. Ward boundary changes in the other metropolitan authorities retain the same number of wards per local authority.

To facilitate the use of the census data by these local authorities Census Area Statistics and Key Statistics tables have been produced for 2004 ward boundaries. New COA to ward lookup tables are supplied for each local authority. The production of 2004 ward boundary geography from these lookup tables provide a ‘best fit’ ward geography not those defined by the Statutory Instrument. The Health GIS Service will be working to produce the new ward boundary files in readiness for dissemination of 2004 health data once mid-year estimates of the ward populations in 2004 are available from ONS.

Figure 01.01 2001 Census Area Statistics & Standard Table Wards with PCTs.

1.3 Super Output Area Boundaries

The English Indices of Deprivation 2004 (ID2004) developed by the Office of the Deputy Prime Minister (ODPM) are the first official statistics to embrace the new family of statistical areas to be known as Super Output Areas (SOAs). SOAs have been developed by ONS by aggregating adjacent COAs through 3 levels of progressively higher area geographies that will nest within CAS wards. The 3 levels of SOA will be known as Lower, Middle and Higher. The Lower level SOAs are used by the ID2004 and designed to provide a minimum threshold population of approximately 1,000 people (average 1,500) or 400 households and consist of up to 5 COAs. Middle level SOAs have a minimum population threshold of 5,000 persons (average 7,500) or 2,000 households and are built from groups of Lower level SOAs constrained to local authority boundaries as used in 2001 census output. When published Upper level SOAs are expected to have a minimum 25,000 population.

Super Output Areas are designed to produce a geography that will remain static and provide consistent reporting areas to all government departments both locally and nationally and to statutory and public agencies. Census day populations for SOAs can be readily aggregated from COA tables to allow statistical reporting yet in calculating ID2004 ODPM uses 2001 mid-year population estimates (MYEs) apportioned to SOAs as the population base for indicators derived from 2001 administrative data. These apportioned MYEs have not as yet been placed in the public domain nor is there any evidence that ONS are to include SOAs in their Small Areas Statistics programme. If ONS is seriously intent on SOAs becoming the standard geography for statistical reporting purposes it is essential that they do this and release annual mid-year estimates by quinery age/sex groups for SOAs.

	Figure 01.02 Lower level SOAs with ward and PCT boundaries - Birmingham and Black Country SHA.
	Figure 01.03 Lower level SOAs with ward and PCT boundaries - Shropshire and Staffordshire SHA.
	Figure 01.04 Lower level SOAs with ward and PCT boundaries - West Midlands South SHA.

1.4 Indices of Deprivation 2004

The Office of the Deputy Prime Minister published the English Indices of Deprivation 2004² (ID2004) on 28th April 2004; they were reissued 17th June 2004 to correct some errors in the calculation of the two new domains – crime & the living environment. The ID2004 are essentially an update of the Indices of Deprivation 2000 (ID2000) as they adopt the same approach, structure and methodology. However, as the ID2004 are based on Lower level SOA geography (rather than wards), include two new domains of deprivation and make use of newly available administrative data sources as indicators for the domains, it is not possible to draw comparisons nor measure change during the period 2000 to 2004.

There are 7 domains measured in the ID2004; income deprivation; employment deprivation; health deprivation and disability; education, skills and training deprivation; barriers to housing & services; incidence of crime; and the quality of the living environment. Two supplementary indices measure income deprivation as it affects children and older people. The 37 indicators contributing to the measurement of the 7 domains were sourced in 2001. Each indicator is specific to one domain and is a direct measure of a major feature of that deprivation across England. Where the indicators used to calculate domain scores are taken from the 2001 census the denominator populations are also taken from the census; where the indicator data is derived from other sources the 2001 mid-year population estimates (MYEs), apportioned to SOAs on the basis of census derived rates are used.

Domain scores and ranks are calculated for each SOA in England. The score is then factored into the composite Index of Multiple Deprivation (IMD2004) for each SOA. IMD2004 scores are ranked across England to allow comparison. Indices of Deprivation have been produced for Wales, Northern Ireland and Scotland but the domains and their indicators are not identical to England so no direct comparisons should be made across the principalities.

IMD2004 scores and ranks have been allocated to 32,482 Lower level SOAs in England. 917 (26.3%) of the SOAs in West Midlands fall into the 20% most deprived SOAs in England.

There is no child poverty index in ID2004 but two domains have specific reference to children: Income deprivation has ‘Income Deprivation affecting Children’ is an index in its own right and Education, Skills & Training has a sub-domain ‘Education deprivation for children/young people’.

	Figure 01.05 ID2004 Education, Skills & Training domain in West Midlands with PCT boundaries.
	Figure 01.06 ID2004 Income deprivation affecting children in the West Midlands with PCT boundaries.

Copyright & Sources: Crown Copyright, OS, ONS, and ODPM.

Reference:

The English Indices of Deprivation 2004: Summary (revised). ODPM, 2004.