text: **The updated modelling approach**
  
  The prison projections form part of the Ministry of Justice’s wider work to 
  develop a consistent and coherent suite of models of the criminal courts and 
  offender management, driven by common projections of demand for the 
  Ministry of Justice’s services. 
  
  The prisons model used to generate the 2014 projections has not changed 
  substantially from that used in the 2013 projections. As in the 2013 projections 
  custodial sentence lengths used in the model are disaggregated by gender, 
  age of the offender and offence type. The total time to be served in prison by 
  projected future prisoners is assigned by matching their gender and age 
  characteristics to relevant distributions of (i) custodial sentence lengths and (ii) 
  the percentage of custodial sentence served. These distributions are derived 
  from data for the period October 2013 to April 2014. This allows us to: 
  
   understand the Criminal Justice System factors which contribute to 
  
  change in the prison population, including sentences lengths issued, 
  the percentage of sentence served in custody, trial court and 
  sentencing court changes, or shifts in the demographic characteristics 
  of defendants; 
  
   model the impact on the prison population of specific Ministry of 
  Justice and other Criminal Justice Agency policy changes; and 