Keith Spicer

Protecting Census 2021 Origin-Destination Data Using a Combination of Cell-Key Perturbation and Suppression

The UK Office for National Statistics (ONS) is intending to produce outputs involving travel to and from different locations (origins and destinations) in 2021, as they have done for previous Censuses. This data poses a particular challenge for protecting against disclosure risk, as categorising respondents on multiple geographical variables yields very sparse tables. This paper explores the disclosure risk and data utility of one option for protecting this data: applying cell-key perturbation (noise), and suppressing the remaining disclosive values. It finds that these methods provide good protection for the data with considerable loss of utility for outputs at low geographies. Whether this is an acceptable approach will be determined by user feedback.