Prison Population Projections 2014 – 2020 
6. Caveats on prison population projections 
The projections presented reflect the impact of three possible trends in 
sentencing, combined with trends in the age, gender and offence of 
defendants entering the system and in the flow of defendants through the 
courts. The impacts of changes to legislation and guidance which took place 
before June 2014 and views of future parole hearing frequency and outcomes 
for indeterminate sentence prisoners have also been taken into account.  
The projections do not reflect the impact of legislative, policy, operational or 
procedural change or guidance for which there is no definite timetable for 
implementation. The projections therefore provide a set of “baseline” 
scenarios against which the impacts of future changes can be assessed.  
Even without these possible changes, the actual future prison population may 
not match any of the projected scenarios. Changes to criminal justice 
processes could influence the numbers of offenders being brought to the point 
of sentence or the way that offenders are managed. Changes to sentencing 
behaviour may also be different from those modelled. Finally, both sentencing 
behaviour and criminal justice processes, as well as policy decisions, can 
respond to a multitude of environmental factors which cannot be anticipated, 
such as high profile criminal cases, events like the August 2011 public 
disorder events, and public debate. 
Assumptions for modelling and scenario development were captured through 
consultation with policy and operational experts at the Ministry of Justice and 
the National Offender Management Service. The assumptions are based on 
analysis (where reliable data are available) and on expert judgement from 
policy makers, key deliverers and system influencers. The assumptions are 
therefore likely to be more robust for those measures and processes that have 
a well-defined boundary than for those that do not.  
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