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Microdata |
What are Samples of Anonymised Records?
The Samples of Anonymised Records (SARs) are a family of
datasets from the 1991 and 2001 Censuses. Each file is a
sample of individual person-level records drawn from the
Census database that has been anonymised. Each file contains
a broad range of socio-demographic characteristics for respondents,
with a particular emphasis on either individual, household, or geographical detail.
The files are designed to ensure that sample members cannot be identified.
In order to achieve this, the amount of detail is restricted on files to a
non-disclosive level, and individual respondents only appear in one file.
Although such measures are taken, the data still looks like that which might
be collected if you were to conduct a survey yourself, and can be analysed
in the same way.
The SARs hold the further advantage of much larger sample sizes than are
typical in alternative survey data sources. For example, the 2001 Individual
Sample of Anonymised Records contains 3% of UK census records, equating to 1.84
million cases. The largest file- the 2001 Small Area Microdata file- is a 5% file
containing nearly three million cases.
The SARs files contain data from one Census only (1991 or 2001).
This contrasts with other individual level (or “microdata”) census
products such as the
Office for National Statistics Longitudinal Study,
which links data over time. However, unlike the Longitudinal Study, most
SAR files can be downloaded and used at your own place of work.
What can the SARs tell us?
Like other microdata files, the SARs enable researchers to analyse data in a very
flexible manner. This enables:
- Grouping of data
- Creation of new variables and application of new definitions
- Definition of tables
- Subsetting
- Multivariate analyses
Because the files are very large, they also permit analyses of relatively
small sub-populations for which it is often difficult to obtain sufficient
sample sizes in other survey data. Consequently, a major use of the SARs has
been for the analysis of individual ethnic groups.
Each of the different SARs files has particular strengths:
The
Individual SAR 2001 is a good all-round easy to access file
with considerable individual level detail, allowing comparisons
between UK countries and regions. For example, Popham (2006) used
this file to demonstrate how Scotland’s higher levels of ill health,
compared to England, can largely be explained through differences
in employment and socio-economic position.
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The 2001 Small Area Microdata enables analyses to be undertaken at
the Local Authority level. This level of geography enables mapping,
local level tabulations, and multivariate analyses including local area
level variables. These data differ from aggregate outputs such as the
Census Area Statistics in that users can look at individual level
characteristics within areas and define area level measures of their
own choice. Users can define and use subsets, and can create new
classifications by grouping existing classifications or combining
information from more than one socio-economic characteristic. |
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The
2001 Special Licence Household SAR contains all individuals within selected
households and links them with a household identifier. This dataset allows the
better description of households, the analysis of household context for individuals,
and the examination of inter-relationships between household members.
The Structure of the Household SAR
Obtaining the data
Most SAR files can be downloaded from the SARs web site at
sars.census.ac.uk.
Files can be accessed in SPSS, Stata, and tab delimited formats. In order to
obtain these files you must first
register with Census.ac.uk.
Files that can be obtained in this way can also be explored online using the
Nesstar tool. This online data exploration and download tool permits users to
browse data and documentation, undertake straightforward analyses, and download
subsets or whole files in a range of formats.
Users of the 2001 Special Licence Household SAR are required to complete a more
comprehensive registration procedure via the
UK Data Archive and to adhere to a
high level of data stewardship. Information about this process is available from
the
UKDA.
What Resources are available?
Data Files:
| Type of File |
Files |
Access |
| End User Licence File 1991 Individual and Household SAR files |
2001 licensed Individual SAR |
2001 Small Area Microdata Registration via Census Registration
System (non-academic users contact CCSR) |
| Special Licence |
2001 Special Licence Household SAR |
Paper registration procedure via UK Data Archive.
See sars.census.ac.uk for further details |
| Controlled Access Microdata |
2001 Individual CAM
2001 Household CAM
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These files, which contain more detail, are available if necessary to users within a safe setting at Census Office premises. Further details and application forms are available on the SARs web site.
The files are managed by the Office for National Statistics |
Associated resources:
A User Guide to the SARs, codebooks and associated documentation are available from the
SARs web site. Users should become familiar with these resources before using the data.
Further Reading
Full information on the SARs is available at sars.census.ac.uk,
including the SARs User Guide, a Getting Started Guide, codebooks, census forms,
software and analysis guides.
Li, Y (2004), Samples of Anonymised Records (SARs) from
the UK Censuses: A Unique Source for Social
Science Research, Sociology 38(3): 553–572