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ONS is aware of the importance to users of samples of anonymised records (SARs) and is confident that fit-for-purpose, appropriately accessible UK microdata files will be made available in 2014.

Three levels of microdata are planned for 2011 Census:

Teaching file

The teaching file is now available.

Formerly called the Public Use file, the primary aim of the teaching file is as an educational tool. The release of this non-disclosive, individual-level file is in line with the government transparency agenda. It is less detailed than the file made available under end-user licence in 2001.

Safeguarded files

One type of safeguarded file will be at the individual person level. The file will to contain a similar level of detail to the 2001 small area microdata, and the individual level SAR, with a maximum sample size of 5 per cent.

The file will either be made available to researchers to hold outside of ONS under strict terms and conditions or will be available within a secure ONS environment. Different access arrangements are being put in place for different types of users to maintain public confidence in ONS protection of confidentiality of the data.

Access to the file outside of ONS will be available through the UK Data Service, but will be limited to users from academia and the public sector. Any other users who wish to access the safeguarded data will have to do so using an alternative method. ONS are exploring the possibility of placing the data in the ONS Virtual Microdata Laboratory (VML), but allowing commercial organisations and other users such as charities and the general public access to the data without the full terms and conditions for access to, and use of, the VML being applied, i.e. it would not be necessary to be registered as an Approved Researcher. Any outputs or analysis produced would be subject to disclosure checks before approval could be given for users to take them outside of the VML.

This file is likely to be released in October 2014. The release date will be published on this page when confirmed. As this file will not be available in the public domain with equal access for all, the release will not be announced in the ONS Release Calendar. More information about the different terms and conditions and how to obtain access to the file will be made available shortly when arrangements have been finalised. 

ONS is also looking at the feasibility of releasing household hierarchical data containing records for all individuals, within a sample of households. Further information on the results of this work will be made available later in 2014.

All files will be subject to being able to apply sufficient disclosure control.  

Secure files

In the long term these anonymised data will be held in a secure environment, ONS's Virtual Microdata Laboratory (VML). However ONS is currently working on a project to replace the VML and an interim VML solution is currently being developed to make the secure data available before the new VML is launched. The interim solution is likely to be available in October 2014, with the new VML likely to be in place at the end of 2014.  

The secure files will generally be similar to the 2001 Controlled Access Microdata Sample (CAMS), both household and individual, and will contain a maximum sample size of 10 per cent. To see the planned microdata product table, download proposed 2011 microdata products (19 Kb Excel sheet) .

Planned features include microdata sets with sample sizes larger than previous censuses, the opportunity for exploratory analysis on rich and flexible datasets, the opportunity to test outputs before requesting commissioned tables, and the ability to perform multivariate statistical analysis, all using records that are comparable with the standard census outputs, since they have the same source.

The household and individual secure files are planned for release in October 2014. This is a delay from the original planned date of August 2014 due to the dependence on the availability of a secure environment in which to store the files. This date is still subject to change and the exact release date will be published on this page when confirmed. As with the safeguarded file, the release of the secure files will not be announced in the ONS Release Calendar.

When the release date is confirmed, information on how to apply for access to the files will be provided on this page. The data will only be available for research purposes conducted by an Approved Researcher. ONS will not accept any requests for access to the data before the release date is confirmed. It is expected that the approval process to gain access to the secure files in the VML will take approximately 2-3 weeks.


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