Prison Population Projections 2014 – 2020 
The approach for the other sub-populations is similar and has not been 
substantially revised since the 2013 publication. The methodology applied to 
each is briefly outlined below. 
The recall population is projected going forward based on time-series data 
available to October 2014.  
For remand prisoners the average time served on remand is calculated from 
the ratio of the remand population to remand receptions. The modelled stock 
of prisoners is calibrated to historical actuals by varying levels of receptions. 
The remand population is generated in two parts both using this approach – 
untried remand and unsentenced remand populations being treated 
separately.  
IPP and life sentence prisoners have an extra section in the stock-flow 
structure which models the indeterminate nature of their sentence lengths. 
Outflows for IPP and life sentence prisoners depend on the tariff lengths they 
receive and on the frequency and outcome of Parole Board hearings. The 
values of these parameters are set and calibrated to reflect the most recent 
data on Parole Board outcomes. 
NOMS have made an agreement with the Home Office to hold an increased 
number of immigration detainees, which are only seen in the final two periods 
of historical data. The projected size of the non-criminal population is therefore 
set equal to the average size of the non-criminal population over the last two 
months of available data. This ensures that the non-criminal projections reflect 
the latest and most accurate count of the non-criminal population. 
The population in prison at the end of each modelled month is aggregated into 
the categories defined by gender, current age group and, for determinate 
sentence prisoners, sentence length band, to produce raw, unadjusted prison 
population projections. 
 
3b) Accounting for the impacts of circumstance, legislation, and for 
seasonal effects  
The raw, unadjusted prison population projections are subject to model 
adjustments to show the impact of certain provisions in the Offender 
Rehabilitation Act 2014, changes at the Verne and the ROTL review.  Model 
adjustments are also used to account for seasonal variation in the population. 
Model adjustments have been applied equally to all the scenarios modelled.  
The Home Office is to gain access to all 580 places at the Verne IRC by 
January 2015. The estimated impacts have been applied to the non-criminal 
projection in the model.  
Provisions in the Offender Rehabilitation Act 2014 will mean that offenders 
sentenced to custodial sentences of less than 12 months will be released 
subject to licence (in the same way as offenders currently released from 
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