Ministry of Justice written question – answered on 18th July 2018
Philip Davies Conservative, Shipley
To ask the Secretary of State for Justice, pursuant to the Answer of 6 July 2018 to Question 158713 on Prison Sentences, how his Department measures the effectiveness of community sentences compared with prison sentences in terms of preventing reoffending.
Rory Stewart The Minister of State, Ministry of Justice
The effectiveness of community sentences compared to prison sentences has been measured by comparing the reoffending outcomes of offenders receiving prison sentences with those of similar offenders who received community sentences. The similarity of offenders is based on available offender demographics, criminal history, risk assessment and management data, and tax and benefit data. More details are provided in chapter 3 of the Ministry of Justice study ‘The impact of short custodial sentences, community orders and suspended sentence orders on re-offending’ published in 2015:
The study used propensity score matching (PSM) to create a counter-factual group, which enabled the outcomes of offenders receiving particular requirements to be compared to outcomes of similar (matched) offenders who did not receive them, and therefore the effect of the requirements to be estimated.
PSM aims to account for all sources of variation between the treatment and control group except for the intervention itself, meaning that any differences in their outcomes should be the result of the intervention.