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Maintaining SNS Geographies

MAINTAINING SCOTTISH NEIGHBOURHOOD STATISTICS GEOGRAPHIES

Purpose

1. New data zone population estimates are due to be published through the Scottish Neighbourhood Statistics (SNS) internet site ( www.sns.gov.uk) on 18 October 2005. The new estimates allow informed decisions to be made on how to maintain the SNS geographies. This note discusses options available and sets out a preferred way forward. Comments on the preferred way forward are welcome from SNS stakeholders. Comments should be sent to neighbourhood.statistics@scotland.gov.uk.

Maintaining data zones: preferred way forward

  • No revisions to data zone geography at this stage
  • Continue to monitor distribution of data zone populations
  • Consider longer term maintenance alongside 2011 Census geography

Data zone population estimates

2. The development of data zone population estimates is a key SNS development which is fundamental to monitoring the impact of a range of policies over time. GROS are developing data zone mid-year population estimates for 2001 through 2004, estimates for 2005 will be available October 2006. Local authority mid-year population estimates are already available through SNS.

3. The data zone geography used 2001 Census output areas as the building block and the majority of data zones had between 500 and 1,000 household residents. GROS are currently quality assuring the data zone population estimates and are now able to provide the likely number of data zones in a range of population bands. It should be noted that some of the larger data zone populations include 'communal establishments', and likely numbers of data zones in 500-1,000 band are not included in the table below.

Likely number of data zones

Population

2001

2002

2004

< 300

0

0

0

300 - 399

0

0

5

400 - 500

34

78

110

1,000 - 1,249

348

389

453

1,250 - 1,500

12

16

37

1,500+

12

11

21

Data zone background

4. The data zone geography is the key small area statistical geography in Scotland. The stability of data zones is of particular importance to monitoring the impact of a range of policies over time. One of the key benefits with the data zones was that they would not be subject to the ongoing administrative or operational change that postcode sectors and electoral wards are. It was always recognised that the size of the data zone meant that it was an ideal building block to allow users to aggregate up to their areas of interest, and also that caution was needed when attempting to interpret and in particular track change at the single data zone level.

5. Data zones are a statistical geography, and early in their development it was recognised that it would be very difficult to develop a single geography which delineated 'natural communities' which would be accepted by all national and local interests. Instead, the approach was to develop a geography with small household populations, which would be relatively socially homogeneous, while at the same time being large enough to allow statistics to be disseminated in terms of confidentiality and reliability.

6. The introduction of the data zone geography introduced a definitive geography that is being widely used across the public sector (and also increasingly academia, voluntary and private sectors) - almost 400 stakeholders now receive the SNS Geography Product CD. This is improving efficiency and is allowing partners to have a common understanding of local issues. A single geography also allows the Scottish Executive to readily produce statistics once and use them many times. This is resulting in improved efficiency and increased use of statistics in policy. Further information about the history of data zones can be found at www.scotland.gov.uk/library5/society/sndata-04.asp.

Revising data zones discussion

7. If data zones were revised then this would be introduced to resolve an issue that affected a very small percentage of the population - making revisions will have little if any affect on policy decisions. Making changes will be resource intensive and it is not clear that this can be justified in light of other SNS priorities. Developing the use of SNS to support national and local policy is now the key priority.

8. The data zone geography is being widely used and a new version of the data zone geography would make it much more difficult to track change. It could also be confusing and add unnecessary complexity to many analysts, policymakers and practitioners. Changes could result in a lack of confidence leading to reduced usage.

9. Making a change to the data zone would mean introducing a new version of the geography, and this would have an impact on the SNS Internet site. Users would not be able to use the SNS internet site to readily track change. Populations can go up and down. There is a risk that one year we merge data zones because of demolitions - the next we split the same data zones because of redevelopment.

10. Revising data zones annually would have an impact on the timely release of small area statistics. Data zone population estimates would be produced in the October following the reference year, the geography would then needed to be changed and the relevant look-up tables to allow aggregation produced and issued, and then the statistics produced.

11. The data zones are fundamentally linked to census geographies and it is recommended that decisions on 'maintaining data zones over the long term' should be made alongside decisions on 2011 census geography. We will also continue to monitor distribution of data zone populations and consult on appropriate action.

Ensuring confidentiality

12. SNS will work with data owners to ensure that the adjustments applied to the data zone level statistics to ensure confidentiality continue, while at the same time ensuring that the statistics are fit for purpose. We will ensure data zones which have relatively small populations, or have had large changes in population are readily identifiable.