This page summarises our Statistical Disclosure Control strategy for Scotland’s Census 2022. Statistical Disclosure Control is needed to prevent the release of confidential information about an individual or household.
NRS has legal obligations to ensure that the privacy of individuals and households is protected in all census outputs. For more information on relevant confidentiality legislation, please see our Confidentiality page.
Statistical Disclosure Control (SDC) refers to the methods that we use to protect the privacy of personal information. This includes making small changes to data, controlling access to data, and controlling the level of detail that is available to census data users.
For Scotland’s Census 2022, we will use three main SDC methods:
- Record Swapping
- Cell Key Perturbation
- Flexible Table builder rules
Record swapping involves swapping the geographical information of a proportion of households. For example, household 1 in area A is swapped with household 2 in area B. In any published census outputs the information from household 1 will be in area B.
Record swapping was the main SDC method used to protect the privacy of households and individuals in outputs from Scotland’s Census 2011.
Cell Key Perturbation
A key innovation for Scotland’s Census 2022 will be the availability of a flexible table builder tool. This will allow users to create their own tables from census data. In order to provide an additional layer of confidentiality protection for tables created via the flexible table builder, we will be using a method of “cell-key perturbation”, whereby small adjustments are made to cells in output tables.
Flexible Table Builder Rules
The flexible table builder will also have rules to ensure that tables containing information that might allow individuals or households to be identified cannot be accessed. For example, tables containing very small cell counts at a given geographic level will not be accessible in the table builder.
We are working with our colleagues at the other UK Census Offices (ONS and NISRA) to ensure that our SDC methods are harmonised at the UK level where appropriate. We coordinate our harmonisation activities at the UK “Outputs & Dissemination Harmonised Working Group”.
For more information on how National Records of Scotland work with the other UK censuses to harmonise our statistical methodology for UK Data Users, as well as share best practice and lessons learned, please see the UK Census Data tab of this website.
We have provided details on our SDC plans for Scotland’s Census at a number of stakeholder events, notably:
- Statistical Disclosure Control and Outputs Event – June 2017
- Here we outlined our Statistical Disclosure Control strategy and early plans for census outputs.
- Statistical Methodology Stakeholder events – February 2020
- At these events we outlined our SDC methodology as part of our broader statistical methodology for Scotland’s Census.
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