Introduction

1.1 Scottish prison population statistics have been published in their current form since 2020. The annual statistical bulletin contains information about the demographics of people in prison, the time they spend there, their sentences and offences, and flows into and out of prison. The statistics are based on administrative data from the Scottish Prison Service (SPS) prisoner records system (PR2).

1.2 Until 2015, Scottish Government published National Statistics based on daily snapshots of data from PR2. Due to a technical issue and a need to use resource in more effective ways, the data transfer of snapshots between SPS and Scottish Government broke down and the statistics were discontinued. This created a large information gap. Scottish Government started work on a new statistical series in 2018, leading to the development of the current method. The new statistics were first released in July 2020 as experimental statistics, to involve users and stakeholders in their development.

1.3 The Cellwise method used to construct the statistics takes historic prison cell occupancy data from PR2 to create a longitudinal spine. Additional information – about warrants, sentences, offences, and liberations (departures from prison) – is then joined to this spine. Several different methods were developed and tested, but Cellwise estimates produced the closest match to previous official statistics and SPS management information.

1.4 The official statistics are not the only source of information about the prison population in Scotland. SPS also publishes a range of datasets and reports, including weekly and annual aggregate management information about the number of prisoners (introduced after the official statistics were discontinued); annual management information about deaths in custody; and a quarterly performance management report with statistics and commentary about trends in the prison population, demographics of prisoners, the impact of the coronavirus pandemic on isolation, absence of prison staff and the prison estate.