The number of prisoners released from young offender institutions following the completion of a determinate sentence between April and September 2008 was approximately 6,400. These data are provisional until final data are published in the Ministry of Justice statistical bulletin Offender Management Caseload Statistics (OMCS).
OMCS 2007 was published on 30 October. Tables 9.1 and 9.2 shows data on discharges from prison. Copies of the bulletin have been placed in the House Libraries and found at the following web link:
http://www.justice.gov.uk/publications/prisonand probation.htm
These figures have been drawn from administrative IT systems, which, as with any large scale recording system, are subject to possible errors with data entry and processing.