Methods

PRISM-R is built from a reproducible data pipeline. Every figure on this site is produced by Python scripts that read publicly available source files and emit flat JSON. The pipeline, the source list and the processed data are open. This page records how PRISM-R works and the decisions behind it.

Published figures versus PRISM-R analysis

PRISM-R draws a clear line between two kinds of number. Where an authoritative body publishes a headline statistic, PRISM-R cites the published figure with explicit provenance rather than substituting its own. The four headline numbers on the home page are cited this way, from Youth Justice Statistics 2024 to 2025. The adult Relative Rate Indices that PRISM-R holds for reference are cited from the Ministry of Justice in the same way: they are derived from data that is not public, so they cannot be reproduced and carry no confidence interval.

Where no published figure exists, PRISM-R produces its own analysis and labels it as such. The road-to-remand cascade, the child-specific Relative Rate Indices, and the remand decision mix by ethnicity are PRISM-R analysis, computed transparently from open data. Every chart on the national picture page is captioned with its source so the distinction is immediate.

A note on terminology

PRISM-R uses current best-practice terminology in its prose, drawing on the racial terminology research published by Action for Race Equality in 2024 and 2025. In the text, children of Mixed Heritage are described as such rather than as "Mixed children", and the residual group is described as children in the Other category.

Charts and data tables retain the source-data category labels exactly: White, Black, Asian, Mixed and Other. These are the labels used by the Youth Justice Board, the Ministry of Justice and the Office for National Statistics in the underlying statistics, and PRISM-R is bound to them for fidelity. The Other category is the ONS residual category: it holds ethnic groups not separately identified, and it is not a single community.

The Relative Rate Index

The Relative Rate Index compares the rate at which an ethnic group experiences an outcome with the rate for the White baseline group. A value of one is parity. The method was recommended in the Lammy Review and is used by the Ministry of Justice. PRISM-R applies it to children specifically, which published official statistics do not.

Each PRISM-R-derived index carries a 95% confidence interval, the Wald interval on the log of the rate ratio. Child custodial sentencing counts are small and unstable year to year, so that index is presented as a three-year pooled estimate; the single-year values are retained for inspection. Confidence intervals are wider for groups with smaller populations, which is a property of disaggregation, not a flaw.

The road-to-remand cascade

The cascade follows children through four decision points: stop and search, arrest, remand, and custodial sentence. Stop and search and arrest rates use the 2021 Census child population as the denominator; remand and custodial sentencing use a count of children already at that stage. A fifth stage, charge, is out of scope for this version: no open data gives child charges by ethnicity at a usable granularity. It is a candidate for a later version.

Disclosure control

PRISM-R applies five disclosure control rules: counts below six are suppressed; secondary suppression protects a single suppressed cell from back-calculation; rates are not shown where the denominator is below 100; suppression already applied in a source is carried through and flagged as inherited; and every suppression decision is logged. National figures rarely trigger suppression because the counts are large; sub-national cells do, and they pass through the same rules.

The full audit trail is published, one record per decision, so a reader can see the rule applied and not only its effect: suppression audit.

Data sources

The headline statistics and the youth justice analysis draw on Youth Justice Statistics 2024 to 2025 (YJB and MoJ). The cascade also uses Home Office Police powers and procedures, year ending March 2025, and the Ministry of Justice statistics on ethnicity and the criminal justice system. Child population is from the 2021 Census. The build manifest records every source with its reference period, publication date, retrieval date and a checksum for each output: build manifest.

What PRISM-R does not yet show

This version works at England and Wales level. It does not yet show remand at local authority level, a geographic map, or post-remand court outcomes by ethnicity. Those require data that is not yet ingested and are planned for later work. The home page figure of 62% of remanded children not receiving a custodial sentence is cited from the published statistics for that reason.

Reproducibility

The pipeline is one command. It runs every ingest and computation step in dependency order, applies disclosure control, and writes the manifest. The processed outputs are deterministic and reproduce byte for byte. The code and the processed data are public: github.com/SGilr/prism-r.

Baseline and tracking

The values shown on PRISM-R as of May 2026 reflect the most recent published Youth Justice Statistics, for the year ending March 2025, and constitute a baseline against which future change will be measured. The Youth Justice White Paper published on 18 May 2026 commits to reducing child remand. PRISM-R will refresh annually within four weeks of each Youth Justice Statistics publication, providing a public, open, reproducible record of the trajectory.

Methodology review

The confidence interval method and the wider analytical approach are to be reviewed by an independent methodologist before launch. A reviewer is being approached. This note will be updated, and signed, once that review is complete.