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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, and it is intended that this will be made available to users via their desktops under strict terms and conditions. More information about these terms and conditions and how to obtain access to the file will be made available shortly. The file is likely 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. ONS hopes to have this file ready for release in September 2014, however, this date is currently provisional and is subject to change.

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 in late summer 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 options for how the secure microdata files can be made available before the new VML is launched, likely to be towards the end of 2014, are being investigated. 

The 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 August 2014, however, this date is not yet confirmed and is dependent on the availability of a secure environment in which to store the files.


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