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Statistical disclosure control

Statistical disclosure control (SDC) concerns safeguarding the confidentiality of the information that the Office for National Statistics (ONS) releases about people and businesses, in order to be compliant with Section 39 of the Statistics and Registration Service Act (SRSA, 2007).

Background and aims

ONS activities involve collecting and processing a wide range of data about individuals and businesses. The ONS SDC Methodology team provides advice to enable ONS, and the wider Government Statistical Service (GSS), to safeguard information given in confidence, in line with the SRSA. The team is developing methods that reduce the risk of confidential information being obtained from published Official Statistics, whether as tables or microdata, while retaining sufficient data utility for the outputs to be useful.

Statistical disclosure control involves modifying data or outputs so that the risk of identifying individuals is reduced to an acceptable level. At a basic level, this involves removing detail (for example, making the categories coarser in some variables) or damaging the data (perturbing values). When disclosure control methods are used, there is always an attempt to find an appropriate balance between the improvement in confidentiality protection and the reduction in data quality.

Recent technological advances have dramatically increased the volume of data available to companies and individuals, especially through the internet. In conjunction with the pressure for open government, these advances have highlighted the importance of the issue of disclosure control.

The increased accessibility translates into higher risk of identifying individuals from published statistics. Therefore, it is essential that the disclosure control measures used to protect the confidentiality of individuals contributing to Official Statistics are adequate and robust.

Current and planned areas of work

There is an ongoing requirement for the development and application of statistical disclosure control methodology to ensure that information attributable to an individual or organisation is not disclosed in any National Statistics publication.

Generally, rare combinations of attributes lead to the identification of individuals, for example, a 16-year-old widow, a 75-year old student, a female miner or a single employer in a specific industry, within a geographic area. Disclosure control methods are applied if ethical, practical or legal considerations require the data to be protected and the risk of identification is sufficiently high. Much of the SDC team's work consists of assessing that risk and applying appropriate methods.

Statistical disclosure control techniques are employed across all areas of National Statistics, and ONS SDC Methodology branch supports business areas both in ONS and across the GSS more generally. More specific current areas of work include:

  • development of methodologies for designing open data sets (microdata released without restriction)

  • intruder testing 

  • protecting longitudinal data

  • the production of synthetic data for research 

The team also provide training in disclosure control for business areas that require it.


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