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Review of the Dissemination of Health Statistics: Confidentiality Guidance. Office for National Statistics, United Kingdom, 2006

At-a-glance
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Link: http://www.statistics.gov.uk/about/Consultations/disclosure.asp

Overview:
The U.K. Office for National Statistics (ONS) is responsible for compiling, analyzing and disseminating economic, social and demographic statistics about the United Kingdom. It administers the statutory registration of births, marriages and deaths in England and Wales and is the home of the National Cancer Database.

This report represents the outcome of a comprehensive review of the dissemination of health statistics. It has been undertaken in two stages. The first part of the review focused on developing guidance for published tables of abortion statistics (see http://www.statistics.gov.uk/downloads/theme_health/abortion_stag_final.pdf). The current report provides more general guidance on disclosure issues around published tables of health statistics. Confidentiality issues concerned with microdata (record-level information) are not covered. This guidance outlines the main steps that a data provider ought to consider in developing specific responses, depending on data type, user requirements and disclosive risk and impact. The report defines three broad risk categories of disclosive risk, which will cover the large majority of requests for tabular data. Recommendations are made on the level of protection required for these three risk categories. Technical advice on the issues raised in this report can be found in the working papers on the above website, including a summary of user and data provider consultations done last summer. A working example of the recommended step-wise approach is provided for one extreme case of sensitive data in the Guidelines for Abortion Statistics.

No single solution is proposed in these guidelines. Instead, guidance is provided on how to develop solutions for different types of datasets based on a logical, step-wise approach. It is more balanced, and less prescriptive than traditional practices that have been adopted across much of the health field, such as the rule of thumb to suppress all values in tables less than 5.

Five working papers, summarized below, accompany this document and topics related to legislation.

Working Paper 1: Confidentiality Protection Legal and Policy Considerations
This working paper provides more information on the legal and policy aspects of confidentiality protection to support the consultation document. Much of the discussion is in regard to UK legislation. There is discussion of situations in which disclosure may occur.

Working Paper 2: Risk Management
This working paper provides more information on issues concerned with risk management to support the consultation document. Included are examples of situations in which risk of disclosure may arise in tabular data. The linking of information is discussed, with particular consideration of disclosure by differencing where tables can be linked to narrow cell descriptions and increase the risk of breaching confidentiality.

Working Paper 3: Disclosure Control Methods
This working paper provides more technical information on disclosure control methods to support the consultation document. These methods can be used to reduce the risk of disclosure in tables of health statistics by disguising those cells determined to be unsafe. The paper includes a general outline of eight methods that can be used to reduce the risk of disclosure. Those methods include table redesign (e.g., aggregation), record swapping (one method of perturbation), suppression, rounding, random rounding, controlled rounding, and Barnardisation.

Working Paper 4: Glossary
The brief glossary contains many acronyms relevant in the UK. Many words and definitions, however, may be helpful in understanding issues and methods for protecting the confidentiality of tabular data.

Working Paper 5: References and Other Guidance
This working paper provides an overview of other guidance and references concerned with protecting the confidentiality of health statistics to support the consultation document for the review of the dissemination of health statistics. Guidelines are summarized and commentary is provided on each guideline. Most information is related to UK public health laws.