text: **3a) Producing prison population projections**
  
  Prison population projections are produced using the Prison Population Stock- 
  Flow Model. The principal sub-populations in prison – determinate sentence, 
  life sentence, imprisonment for public protection (IPP) and remand – are 
  modelled using stock-flow structures based on the generic structure shown in 
  Figure B2. The stock-flow structures model the flow of offenders into and out 
  of prison and count the resulting prison population at the end of each month. 
  
  **Figure B2: Generic stock-flow structure in the Prison Population Stock-Flow**
  **Model**
  
  Prison Population 
  Prison Population 
  
  Discharges 
  Discharges 
  Receptions / Pre-tariff ends 
  Receptions / Pre-tariff ends 