A proven reoffence is defined as any offence committed within 12 months of release, conviction or caution that leads to a subsequent court conviction, caution, reprimand or warning within the 12 months or within a further six month waiting period to allow the offence to be proven in court.
Proven reoffending is measured using a number of data sources including an extract of the Police National Computer (PNC) held by the Ministry of Justice (MOJ).
A certain proportion of offenders who could not be matched to the PNC were excluded from the estimates. Therefore, these numbers do not represent all proven offenders. Administrative data sources have been reported as recorded and as such, some inherent inaccuracy may exist.
There are 2 sets of data for this measure:
- data from the period January to March 2011 through the period July to September 2015 are from the Inmate Information System and provide a comparable time series over this period
- the latest data – for October to December 2015 – are from the established case management system for use by probation services and should not be compared with previous periods
Further information about the change of data source and methodology can be found in MOJ’s publication How the measure of proven reoffending has changed and the effect of these changes (PDF).
The estimates in this measure can be used to calculate a relative rate index of the proportion of offenders who reoffend, as published in the Lammy review. The index provides an estimate of how more likely or less likely offenders from a particular ethnic group are to reoffend, relative to white offenders. To calculate the relative rate index, divide the proportion of offenders who reoffend for the ethnic group of interest by the proportion of offenders who reoffend for the White group.
Suppression rules and disclosure control
Proportions and averages based on fewer than 30 offenders are removed as they make data unreliable. Number of reoffenders, reoffences and previous offences based on fewer than five offenders are suppressed. This is to prevent the disclosure of individual information.
Percentages are rounded to 1 decimal place.
Reoffences per reoffender are rounded to 2 decimal places.