Prison Population Projections 2014 – 2020 
longer custodial terms). During the licence period, offenders are under 
probation supervision and can be subject to various conditions for the 
purposes of rehabilitation and public protection. The 2014 Act will also 
introduce a new post-sentence supervision period that follows licence for 
offenders released from custodial sentences of less than 2 years. Breaches of 
these licence or supervision periods could result in the offender being recalled 
or committed to custody, impacting the prison population. The estimated 
impacts have been applied to the recall populations in the model. 
The impact of the ROTL review has also been included as a post model 
adjustment. The review decided that all offenders who have previously 
absconded will no longer be allowed to return to the open estate or be 
released on temporary licence except in exceptional circumstances. Alongside 
protecting the public this may have the impact of delaying the release decision 
for such offenders impacting the prison population. The estimated impacts 
have been applied to the determinate population with sentences of greater 
than 12 months and the indeterminate population. 
Other ongoing changes within the system – included in previous published 
projections as model adjustments – are assumed to be captured in the past 
data and the trends detected therein. 
Custodial conviction projections for each sub-population were smoothed using 
a centred 12 month average. No seasonality in prison receptions and 
discharges was modelled explicitly. Seasonality was measured in the historical 
prison population and applied as a series of percentage adjustments to the 
final population projections.  Seasonal factors for a set of sub-population 
categories (Remand, Determinate by sentence length band and Recall) were 
identified for each month by measuring statistically significant deviations from 
a centred 12 month average. 
 
 
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