# Prison Population Projections 2013 - 2019 England And Wales

 
Ministry of Justice Statistics Bulletin Published 7th November 2013 Decorative image

## Contents

| Key points                                                                     | 2   |
|--------------------------------------------------------------------------------|-----|
|                                                                                |     |
| 1.                                                                             |     |
|                                                                                |     |
| Introduction                                                                   | 3   |
|                                                                                |     |
| 2.                                                                             |     |
|                                                                                |     |
| Prison population June 2012 to June 2013                                       | 5   |
|                                                                                |     |
| 3.                                                                             |     |
|                                                                                |     |
| Modelling methodology and projection scenarios                                 | 7   |
|                                                                                |     |
| 4.                                                                             |     |
|                                                                                |     |
| Results                                                                        | 9   |
|                                                                                |     |
| 5.                                                                             |     |
|                                                                                |     |
| Caveats on prison population projections                                       | 12  |
|                                                                                |     |
| Appendix A: Additional tables                                                  | 14  |
|                                                                                |     |
| Appendix B: Testing the validity of 2013-2019 prison population projections 20 |     |
|                                                                                |     |
| Appendix C: Detail of models, scenarios and assumptions                        | 22  |
|                                                                                |     |
| Appendix D: Stakeholders consulted about scenarios                             | 29  |
|                                                                                |     |
| Contact Points for further information                                         | 30  |
|                                                                                |     |
|                                                                                |     |
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|                                                                                |     |

## Key Points

This bulletin presents projections of the prison population in England and Wales from November 2013 to December 2019. The prison population projections are based on assumptions about future custodial convictions and incorporate the anticipated impacts of selected policy and procedural initiatives. The prison population projections are produced using a model of flows of offenders into and out of prison which counts the resulting prison population each month. Three projected scenarios have been modelled. They track the impact of three different sentencing trends on custodial convictions, custodial sentence length and hence on the resulting prison population. These correspond to (though do not use the same assumptions as) the "Scenario 1", "Scenario 2" and "Scenario 3" scenarios used in the 2012 projections. Other impacts included in the projections, such as those of changing legislation, changing procedures and new sentencing guidelines are applied equally to all three scenarios. The projected prison populations under each scenario are given in Table 1. By the end of June 2019, the prison population is projected to be 77,300 in the Scenario 1 projection, 81,800 in the Scenario 2 projection and 86,600 in the Scenario 3 projection. 

Sentencing Scenarios
Scenario 1
Scenario 2
Scenario 3
Jun-14
82,600
83,400
84,300
Jun-15
80,100
82,100
84,300
Jun-16
79,000
82,000
85,000
Jun-17
78,000
81,600
85,400
Jun-18
77,300
81,500
85,800
Jun-19
77,300
81,800
86,600
 

The assumptions informing these projections, and therefore the projections themselves, are subject to significant uncertainty. This is represented by the three scenarios, with each scenario being only as likely as the assumptions which inform it. Indeed, the 2013 Scenario 2 projection is lower than last year's Scenario 2 (central) projection largely due to the decline in court disposals seen in the financial year 2012/2013. The assumptions used are based on extensive consultation (see Appendix D for a list of those consulted), and observed data trends.  A comparison between projected and actual prison population for September 2013 is given in Appendix B, but this publication does not anticipate which of the modelled scenarios is most likely to occur in the future. 

## 1. Introduction

This bulletin presents prison population projections for England and Wales from November 2013 to December 2019. The projections are produced to aid development, capacity planning and resource allocation within the Criminal Justice System (CJS) and the National Offender Management Service 
(NOMS). The latest published useable operational capacity (1 November 
2013) is 86,0021. 

Three projections of the prison population have been agreed through a consultative process. These projections track the impact of three different trends in sentencing on custodial convictions, custodial sentence length and hence on the resulting prison population. These scenarios also take into account drivers which impact equally on each scenario:  

 
trends in the age, gender and offence of defendants entering the 
system and in the flow of cases through the courts; 
 
views of future parole hearing frequency and expected outcomes for 
indeterminate (Life and Indeterminate for the Public Protection) sentences;  
 
the opening of The Verne as an immigration removal centre in 
February 2014; 
 
data recording changes for foreign nationals;  
 
the assumed impact of the changes to court committals; and 
 
the impact of the Legal Aid, Sentencing and Punishment of Offenders 
Act which achieved Royal Assent in May 20122. 
The prison projections model is part of wider work within the Ministry of Justice 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 custodial convictions model uses projections of numbers of defendants entering the criminal courts and takes into account: 

 the age, gender and offence of defendants entering the system;  the flow of cases through the courts; and 
                                                
 
 the sentences which concluded cases attract, in order to project volumes of defendants being given a custodial sentence. The prison population projections model takes projections of custodial convictions, converts them to projections of prison receptions and then models the amount of time that offenders spend in prison to calculate the resulting prison population. The benefits of this method are that it allows us to: 

 
explicitly project custodial convictions (rather than just convictions);  
understand the Criminal Justice System factors which contribute to 
change in the prison population, be they time served, sentences given, trial and sentencing court changes or shifts in defendant demographics; and  
more easily model the impact on the prison population of specific 
Ministry of Justice and other Criminal Justice Agency policy changes relating to specific offences or specific sentences.  
 Appendix C provides details of the methods used to produce the prison population projections and the assumptions behind them. 

## 2. Prison Population June 2012 To June 2013

The 'Story of the Prison Population 1993 to 2012 is an in-depth look at what happened to the prison population between 1993 and 2012 and the major factors contributing to the changes.3  
The prison population grew rapidly between 1993 to 2008 - an average of 4% a year.  This rapid rise was driven by: 

 
Increased numbers of people sentenced to immediate custody from 
1993 to 2002. 
 
Increases in the average custodial sentence length and increased use 
of indeterminate sentences. 
 
Increase in numbers recalled to prison following breaches of the 
conditions of licence and these offenders spending longer in prison once recalled. 
 
The rise in the prison population slowed considerably from the summer of 2008, in part due to the introduction of the Criminal Justice and Immigration Act (CJIA) 20084, which changed sentencing and offender management in ways which helped to reduce growth in the prison population. This flatter trend continued until the public disorder seen in UK cities from 6 to 9 August 2011 which had an immediate but temporary impact on the prison population. During 2012 and into 2013, the prison population began to fall due to a falling remand population and a continued decline in the number of under 18s in custody.  The falling remand population during 2012 reflected falling volumes going through the courts plus the introduction, in December 2012, of measures restricting the use of remand for all offenders who would be unlikely to receive a custodial sentence.5 

## 

Table 2 summarises these changes. 

Offender Management Statistics
Year on year % 
difference
Start of Year
End of Year
June 2005 to June 2006
76,190
77,982
2.4%
June 2006 to June 2007
77,982
79,734
2.2%
June 2007 to June 2008
79,734
83,194
4.3%
June 2008 to June 2009
83,194
83,454
0.3%
June 2009 to June 2010
83,454
85,002
1.9%
June 2010 to June 2011
85,002
85,374
0.4%
June 2011 to June 2012
85,374
86,048
0.8%
June 2012 to June 2013
86,048
83,842
-2.6%

## 3. Modelling Methodology And Projection Scenarios

The method used for generating projections of the prison population in England and Wales for the 2013-2019 projections is consistent with the approach used to generate the 2012-2018 projections published at 1 November 2012. At the core of the method is a model of flows of offenders into and out of prison which counts the resulting prison population each month for sentenced, recall and remand prisoners. Inputs to the prison projections model include projections of future custodial convictions. These are generated from time series projections of numbers of defendants entering the criminal courts and take into account the age, gender and offence of defendants entering the system, the flow of cases through the courts and the sentences which concluded cases attract. The prison projections model monitors the sizes of the sentenced, recall and remand prison populations. These populations depend on the inflows defined above and the outflows.  These outflows are defined by observed distributions of custodial sentence lengths, and percentage of custodial sentence served for subsets of these populations. The model also simulates the ageing of the prison population over time. The results of the prison projections model are supplemented with an estimate of the future non-criminal and fine defaulter populations, which is based on the average of published data from January to June 2013. 

The projection model is based on data up to June 2013 from various sources including court proceedings and performance data, sentencing data and prison receptions and population data. Three projected scenarios have been modelled as shown in Tables 3a and 3b. These scenarios track the impact of three different incremental changes in sentencing behaviour up to March 2016, where the scenario changes are flatlined: 

 
The Scenario 1 projection assumes that decreasing trends in receipts 
to courts double, and disposals will fall in line with these trends. The average length of sentence also decreases following a reversal of current observed trends.  
 
The Scenario 2 projection assumes that recent trends in receipts will 
continue and disposals will stay constant with the previous year (April 2012 - March 2013).  The average length of sentence remains consistent with that seen in the previous 15 months.  
 
The Scenario 3 projection assumes that the recent decreasing trends 
will be reversed going forwards and disposals will rise in line with this change.  The average length of sentence also increases following current observed trends. 
The three projected scenarios also incorporate the impact of: 

 
trends in the age, gender and offence of defendants entering the 
system and in the flow of cases through the courts; 
 
views of future parole hearing frequency and expected outcomes for 
indeterminate sentences;  
 
the opening of The Verne as an immigration removal centre in 
February 2014; 
 
data recording changes for foreign nationals;  
 
the assumed impact of changes to court; and 
 
the impact of the Legal Aid, Sentencing and Punishment of Offenders 
Act which achieved Royal Assent in May 2012. 
The scenarios modelled are not predictions of what will happen to the prison population, but rather indications of what the prison population would look like if scenario conditions were to be fulfilled. The scenarios do not represent bounds on our projections of the prison population. 

Average year on year percentage change in custodial convictions 2013 - 2016
21 years and over
18-20 years
Less than 18 years
Male
Female
Male
Female
Male
Female
Scenario 2
-1%
0%
0%
3%
-1%
0%
Sentencing Trends
 
Sentencing Trends
Average year on year percentage change in custodial convictions 
Year on year percentage change in 
average custodial sentence length 
from Scenario 2
21 years and over
18-20 years
Less than 18 years
Male
Female
Male
Female
Male
Female
Scenario 1
-2%
-1%
-2%
-2%
-5%
-7%
-1%
Scenario 2
0%
0%
0%
0%
0%
0%
0%
Scenario 3
2%
1%
2%
1%
4%
0%
1%
 

The modelling methodology, projection scenarios and assumptions used are described in detail in Appendix C. 

## 4. Results

The Scenario 1 projection estimates that the prison population will fall to 82,600 by the end of June 2014 and to 77,300 by the end of June 2019. The Scenario 2 projection estimates that the prison population will fall to 83,400 by the end of June 2014 and to 81,800 by the end of June 2019. The Scenario 3 projection estimates that the prison population will fall to 84,300 by the end of June 2014 and subsequently rise to 86,600 by the end of June 2019.   Chart 1 presents the projected scenarios to show changes in the prison population from November 2013. Appendix A contains tables for annual projected end of June populations, average financial year populations and total monthly populations for each scenario. Sub-population figures are given for: determinate sentences; indeterminate sentences; remand; recalls; non-criminals; fine defaulters; 15-17 year olds; females 18 and over; males 18-20 and males 21 and over (determinates, indeterminates, recalls and remand).  
The projected trends reflect the cumulative impacts of the various circumstantial, sentencing, legislative and procedural assumptions that are used to generate the projections. The seasonal pattern reflects the dip in the prison population which is always seen around the Christmas period. In the Scenario 2 projection, the prison population is expected to fall to 83,400 by June 2014, due to the continued impact of the Legal Aid, Sentencing and Punishment of Offenders Act and the decrease in court disposals seen in the financial year 2012/13.  The projected population in this scenario is then expected to fall 1.5 per cent by June 2015, before fluctuating slightly (between -0.5 and 0.3 per cent year on year) until 2019.  The projected decrease seen to 2014 is primarily driven by a reduction in court disposals and the continued effect of the Legal Aid, Sentencing and Punishment of Offenders Act.  The projected decreases seen after 2014 are small as the decline is counteracted by an increase in the longer term determinate population (4+ years).  It should be noted that the Legal Aid, Sentencing and Punishment of Offenders Act has caused those that would have received an Imprisonment for Public Protection (IPP) sentence to now receive a determinate sentence.  This has created a shift from the indeterminate population to the determinate population, which affects all three scenarios. In the Scenario 1 projection, the prison population is expected to fall to 82,600 by June 2014.  The projected prison population in this scenario is then expected to fall (between 3.0 and 0.1 per cent year on year) to 2019.  This decrease can be attributed to a projected decrease in the number of immediate custodial convictions and shorter custodial sentence lengths under this scenario. In the Scenario 3 projection, the prison population is expected to be at 84,300 in June 2014 and then expected to grow each year (between 0.1 and 0.9 per cent).  These rises are the result of increases in the level of custodial sentences and the increase in custodial sentence length under this scenario, although this is moderated by the downward effects of the Legal Aid, Sentencing and Punishment of Offenders Act. At the end of September 2013 the published prison population was within 2.1 per cent of the Scenario 2 projection, and within 1.6 per cent of the Scenario 1 projection and 2.6 per cent of the Scenario 3 projection.  Most of this deviation is located in the projected remand population, which accounts for 1.2 
percentage points of the 2.1 per cent difference from Scenario 2.  This does not necessarily mean the prison population will track against either the Scenario 2 or Scenario 1 projection going forward. Differences could be explained by changes, different to those projected, in overall demand, offence mix, age and gender of defendants, court routes, custody rates or sentence lengths. A discussion of the extent to which the actual prison sub-populations have tracked the Scenario 2 projection can be found in Appendix B. Chart 2 plots the 2013 Scenario 2 projection against the three 2012 prison population projections. The 2013-2019 Scenario 2 projection is consistent with the 2012 Scenario 2 projection at the November 2013 point, but continues to fall slightly.  Going forward the Scenario 2 projection sits between the 2012 Scenario 1 (the lower) and Scenario 2 (the central) projections.  A comparison of end of June figures from the 2012 and 2013 projections can be found in Appendix A. The lower level of the new projections can be attributed mainly to a decrease in the number of custodial convictions in 2012/13. 

## 5. Caveats On Prison Population Projections

The projections presented here are a set of scenarios which 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 2013 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. Other impacts included in the projections (such as changing legislation and changing procedures) are applied equally to all three scenarios. 

Assumptions for modelling and scenario development were captured through a consultative process that included all major stakeholders (see Appendix D). 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. For the total prison population, the Scenario 2 projection for September 2013 is within 2.1 per cent of published data6.  
Data used in the model have been derived from various sources, including court proceedings and performance data, sentencing data and prison receptions, and population data. Due to technical problems relating to the supply of data for statistical purposes, some of these data were unavailable from July 2009 to February 2010 and others from July 2009 onwards. This means certain data has been estimated by extrapolating between past and current data and other data has been estimated from headline totals which were unaffected by these problems. 

## Appendix A: Additional Tables7

Annual tables of overall projected prison population 

Sentencing Scenarios
Scenario 1
Scenario 2
Scenario 3
Jun-14
82,600
83,400
84,300
Jun-15
80,100
82,100
84,300
Jun-16
79,000
82,000
85,000
Jun-17
78,000
81,600
85,400
Jun-18
77,300
81,500
85,800
Jun-19
77,300
81,800
86,600
 
Sentencing Scenarios
Scenario 1
Scenario 2
Scenario 3
2014/15
81,800
83,200
84,600
2015/16
80,100
82,400
84,900
2016/17
79,200
82,400
85,600
2017/18
78,100
81,900
85,800
2018/19
77,600
81,900
86,400
 
Sentencing Scenarios
2012
2013
Difference
Jun-13
84,600
--
--
Jun-14
84,300
83,400
-1.0%
Jun-15
84,400
82,100
-2.8%
Jun-16
84,700
82,000
-3.3%
Jun-17
85,300
81,600
-4.5%
Jun-18
85,600
81,500
-5.0%
Jun-19
--
81,800
--
 

                                                
 
Annual tables of subgroups within the overall projected prison population 

Sentencing Scenarios
Scenario 1
Scenario 2
Scenario 3
Jun-14
51,600
52,600
53,600
Jun-15
49,800
52,200
54,500
Jun-16
49,400
52,600
55,800
Jun-17
48,900
52,700
56,700
Jun-18
48,800
53,100
57,600
Jun-19
49,000
53,700
58,600
 
Sentencing Scenarios
Scenario 1
Scenario 2
Scenario 3
Jun-14
12,300
12,600
12,900
Jun-15
11,600
11,900
12,300
Jun-16
11,000
11,400
11,700
Jun-17
10,500
10,800
11,200
Jun-18
10,000
10,400
10,800
Jun-19
9,700
10,100
10,500
 
Sentencing Scenarios
Scenario 1
Scenario 2
Scenario 3
Jun-14
11,100
10,600
10,100
Jun-15
11,300
10,500
9,800
Jun-16
11,400
10,600
9,900
Jun-17
11,300
10,500
9,800
Jun-18
11,300
10,600
9,800
Jun-19
11,300
10,600
9,900
 
Sentencing Scenarios
Scenario 1
Scenario 2
Scenario 3
Jun-14
5,100
5,100
5,100
Jun-15
4,800
4,900
5,100
Jun-16
4,800
4,900
5,100
Jun-17
4,800
5,000
5,200
Jun-18
4,700
4,900
5,100
Jun-19
4,700
4,900
5,100
 
Sentencing Scenarios
Scenario 1
Scenario 2
Scenario 3
Jun-14
2,400
2,400
2,400
Jun-15
2,400
2,400
2,400
Jun-16
2,400
2,400
2,400
Jun-17
2,400
2,400
2,400
Jun-18
2,400
2,400
2,400
Jun-19
2,400
2,400
2,400
Sentencing Scenarios
Scenario 1
Scenario 2
Scenario 3
Jun-14
100
100
100
Jun-15
100
100
100
Jun-16
100
100
100
Jun-17
100
100
100
Jun-18
100
100
100
Jun-19
100
100
100

 
                                                
 

Males 21 years and over
Total Population
Determinates
Scenario
Scenario 1
Scenario 2
Scenario 3
Scenario 1
Scenario 2
Scenario 3
Jun-14
72,500
73,200
73,900
45,100
45,800
46,600
Jun-15
70,600
72,200
74,000
43,700
45,600
47,500
Jun-16
69,800
72,300
74,800
43,500
46,100
48,700
Jun-17
68,800
71,900
75,100
43,100
46,300
49,500
Jun-18
68,200
71,800
75,500
43,000
46,600
50,400
Jun-19
68,100
72,100
76,200
43,200
47,200
51,300
Indeterminates
Remand
Scenario
Scenario 1
Scenario 2
Scenario 3
Scenario 1
Scenario 2
Scenario 3
Jun-14
11,700
12,000
12,300
9,000
8,600
8,200
Jun-15
11,000
11,400
11,700
9,200
8,500
8,000
Jun-16
10,500
10,800
11,200
9,200
8,600
8,000
Jun-17
10,000
10,300
10,700
9,200
8,500
7,900
Jun-18
9,500
9,900
10,300
9,200
8,600
8,000
Jun-19
9,200
9,600
10,000
9,200
8,600
8,000
Recall
Non Criminal
Scenario
Scenario 1
Scenario 2
Scenario 3
Scenario 1
Scenario 2
Scenario 3
Jun-14
4,600
4,600
4,600
2,100
2,100
2,100
Jun-15
4,300
4,500
4,600
2,200
2,200
2,200
Jun-16
4,300
4,400
4,600
2,200
2,200
2,200
Jun-17
4,300
4,500
4,600
2,200
2,200
2,200
Jun-18
4,300
4,400
4,600
2,200
2,200
2,200
Jun-19
4,200
4,400
4,600
2,200
2,200
2,200
 
Sentencing Scenarios
Scenario 1
Scenario 2
Scenario 3
Jun-14
5,500
5,600
5,700
Jun-15
5,200
5,500
5,700
Jun-16
5,100
5,400
5,700
Jun-17
5,100
5,400
5,800
Jun-18
5,100
5,400
5,800
Jun-19
5,000
5,400
5,800
 

 

Sentencing Scenarios
Scenario 1
Scenario 2
Scenario 3
Jun-14
3,700
3,700
3,800
Jun-15
3,500
3,600
3,700
Jun-16
3,400
3,500
3,600
Jun-17
3,400
3,500
3,700
Jun-18
3,400
3,500
3,700
Jun-19
3,400
3,500
3,700
Sentencing Scenarios
Scenario 1
Scenario 2
Scenario 3
Jun-14
800
900
900
Jun-15
800
800
900
Jun-16
800
800
900
Jun-17
700
800
900
Jun-18
700
800
900
Jun-19
700
800
900
 

                                                
 
Monthly tables of overall projected prison population 

|            |            | Sentencing Scenarios   | Sentencing Scenarios             |
|------------|------------|------------------------|----------------------------------|
| Scenario 1 | Scenario 2 | Scenario 3             | Scenario 1 Scenario 2 Scenario 3 |
| Nov-13     | 85,800     | 86,200                 | 86,700                           |
| Dec-13     | 82,300     | 82,700                 | 83,300                           |
| Jan-14     | 83,500     | 84,100                 | 84,700                           |
| Feb-14     | 83,400     | 84,100                 | 84,800                           |
| Mar-14     | 82,900     | 83,700                 | 84,600                           |
| Apr-14     | 82,300     | 83,300                 | 84,300                           |
| May-14     | 82,300     | 83,400                 | 84,600                           |
| Jun-14     | 82,600     | 83,400                 | 84,300                           |
| Jul-14     | 82,800     | 83,800                 | 84,900                           |
| Aug-14     | 83,300     | 84,500                 | 85,700                           |
| Sep-14     | 82,900     | 84,200                 | 85,500                           |
| Oct-14     | 82,800     | 84,200                 | 85,700                           |
| Nov-14     | 82,200     | 83,800                 | 85,400                           |
| Dec-14     | 79,100     | 80,800                 | 82,600                           |
| Jan-15     | 80,300     | 82,100                 | 84,000                           |
| Feb-15     | 80,400     | 82,400                 | 84,400                           |
| Mar-15     | 80,200     | 82,300                 | 84,300                           |
| Apr-15     | 79,900     | 82,100                 | 84,400                           |
| May-15     | 80,000     | 82,200                 | 84,400                           |
| Jun-15     | 80,100     | 82,100                 | 84,300                           |
| Jul-15     | 80,500     | 82,700                 | 85,000                           |
| Aug-15     | 81,300     | 83,500                 | 85,800                           |
| Sep-15     | 81,200     | 83,500                 | 85,800                           |
| Oct-15     | 81,000     | 83,500                 | 85,900                           |
| Nov-15     | 80,800     | 83,200                 | 85,800                           |
| Dec-15     | 77,900     | 80,400                 | 83,000                           |
| Jan-16     | 79,300     | 81,800                 | 84,500                           |
| Feb-16     | 79,400     | 82,100                 | 84,800                           |
| Mar-16     | 79,300     | 82,000                 | 84,700                           |
| Apr-16     | 79,100     | 82,000                 | 84,900                           |
| May-16     | 79,200     | 82,100                 | 85,000                           |
| Jun-16     | 79,000     | 82,000                 | 85,000                           |
| Jul-16     | 79,500     | 82,600                 | 85,600                           |
| Aug-16     | 80,300     | 83,500                 | 86,500                           |
| Sep-16     | 80,300     | 83,400                 | 86,500                           |
| Oct-16     | 80,300     | 83,400                 | 86,700                           |
| Nov-16     | 80,000     | 83,300                 | 86,600                           |

## Appendix B: Testing The Validity Of 2013-2019 Prison Population Projections

The figures in this bulletin are not predictions of the prison population - they are scenarios showing what the future prison population would look like under various circumstances. However, comparing the projections with actual figures allows us to assess whether the actual prison population is aligned to any of the projections and whether the corresponding scenario assumptions hold true. As the model provides population figures for September 2013 we can compare our projections with the actual prison population at this point. Table B1 shows the percentage difference between the Scenario 2 projection and published population figures10 for September 2013. 

September 2013
Total Prison Population
2%
Sub Population
September 2013
Determinates
1%
Indeterminates
2%
Remand
8.5%
Recall
2%
Non Criminal
1%
Fine Defaulters
20%
Males 21 and over (Total)
2%
Males 21 and over (Determinates)
1%
Males 21 and over (Indeterminates)
2%
Males 21 and over (Remand)
8%
Males 21 and over (Recall)
3%
Males 18-20 (Total)
1%
Females 18 and over
2%
15 - 17 year olds
7%
 

The Scenario 2 projection is in line with published figures for September 2013 which deviate no more than 2.1 per cent from the projection, with the overall sub-population of determinate, indeterminate and recall populations deviating ±2 per cent. 

 
Most of the total population deviation occurs within the projected remand population (8.5 per cent), which accounts for 1.2 per cent of the total 2.1 per cent difference in Scenario 2.  Past projections of remand have not provided any greater accuracy for this population. For example, projections published in 2012 predicted a central value which was higher than published figures by 6 per cent and in the 2011 published projections it deviated by -4 per cent. Assumptions used to model the remand population may be developed further in future. 

Although the fine defaulter population shows a large percentage difference from the Scenario 2 projection this is only actually around a 20 place difference, due to the small numbers involved. The sub-populations provided for adult males are within ±3 per cent for all populations, except remand.  The male 18-20 and female 18 and over populations deviate by at most 2 per cent.  This has been influenced by the over-estimation of the remand population and the small population size. The 15-17 year old population is a small population which is difficult to model accurately. Currently, the medium projection for 15-17 year olds deviates by around 60 places (7 per cent difference). The 2012 projections provided no greater accuracy, with a deviation of 160 places. 

## Appendix C: Detail Of Models, Scenarios And Assumptions 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 2013 projections has not changed substantially from that used in the 2012 projections. As in the 2012 projections, gender and age are also used in the allocation of custodial sentence lengths.  These custodial sentence lengths are assigned to defendants by matching these characteristics to observed distributions of custodial sentence lengths and the percentage of custodial sentence served, which are taken from January 2012 to March 2013 data.  This allows us to: 

 
understand the Criminal Justice System factors which contribute to 
change in the prison population, be they time served, sentences given, trial court and sentencing court changes, or shifts in the demographic characteristics of defendants;  
 
more easily model the impact on the prison population of specific 
Ministry of Justice and other Criminal Justice Agency policy changes; and 
 
quantify some of the uncertainty around the time a defendant serves in 
prison.  
 

## Overview Of The Modelling Approach

Central to the modelling approach is the Prison Population Stock-Flow model. Projections of future custodial convictions are fed into this model and outputs are adjusted to account for the impact of changes in legislation and process on the prison population, as shown in Figure C1, and described below. 

Prison Projections Prison Projections
3
2
Key
1
Model Model Input Output Output

## 1) Producing Projections Of Defendants Proceeded Against

Projections of defendants proceeded against at court are chosen as the entry point to the modelling system because this is the entry point of defendants into the MoJ's area of responsibility.  Underlying crime levels and the activities of the police and CPS will have an impact on the volume of defendants proceeded against. Consultation has taken place with the Home Office and CPS to understand these upstream impacts. The Demand Projections Model produces baseline projections of all defendants proceeded against at court for 12 high-level offence categories based on historical time series data (January 2001 to March 2013) at a monthly resolution out to 2019. These are further sub-divided by age, gender and sub-offence using a top-down forecasting approach. The demand projections are based on time series forecasting methods, including moving averages, exponential smoothing and ARIMA.  Each offence category and its sub-categories are forecasted separately.  Statistical error measurement scales and expert judgement are used in combination to find the most appropriate forecast model.  Seasonality is applied based on the analysis of autocorrelations. It should be noted that these projections can not be expected to track actual volumes of defendants proceeded against if there is any sudden or cumulative change which takes demand volumes or offence mix well outside the trends seen historically. 

## 2) Converting The Demand Projections Into Custodial Convictions

A Courts and Sentencing Module converts the demand projections into a set of projections of disposals by disposal type (including custodial convictions), offence, sex and age band at monthly resolution.  These projections of custodial convictions by sex, age and offence type are used as a key input for the Prison Population Stock-Flow model. The Courts and Sentencing Module is a combination of the Magistrates' and Crown Court Workload Models and the Sentencing Module.  The demand projections are used as an input into a Magistrates' Workload Model, which uses historical data to split defendants into court routes (Table C1) and tracks their flow through the system.  This informs the forecast for the number of cases for trial or sentence that will be received in the Crown Court Workload Model. The Crown Court workload model takes forecasts of caseload and assigns various attributes (e.g. early guilty plea, remand status) to estimate likely hearing times and to prioritise the flow of cases through the system.  The cases disposed of are then converted to the number of defendants disposed of using the observed ratio between cases and defendants for the time period of April 2012 to March 2013. 

The key assumptions that are used in the Courts and Sentencing Module are: 

 
that there is no prioritisation of any age or sex group within the 
Magistrates' and Crown Court;   
 
the number of working days in each month is the primary driver of 
seasonality within the Magistrates' and Crown Court; 
 
no change in offence type occurs as cases move through the system; 
 
defendants that are tried at the Magistrates' Court proceed to 
sentencing without delay; 
 
delays within the Magistrates' Court are not significant for the monthly 
timescales used in the modelling; and 
 
a Magistrates' Court backlog will not develop during the forecast 
period. 
The Sentencing Module takes the number of defendants disposed of in the Magistrates' Workload Model and the Crown Court Workload Model and applies sentencing splits using court proceedings data from January 2004 to March 2013 at a quarterly resolution.  This results in a set of projections as broken down in Table C1.  These are aggregated providing forecasts for each offence, gender, age and disposal category, which are used as the custodial conviction projections. 

| Offence Type                | Gender   | Age Band   | Court Route   |
|-----------------------------|----------|------------|---------------|
| Burglary                    | Male     | Age 10-17  | MC            |
| Discharge                   |          |            |               |
| Criminal Damage             | Female   | Age 18-20  | MCCC          |
| Fine                        |          |            |               |
| Fraud and Forgery           | Age 21+  | CC         |               |
| Community Sentence          |          |            |               |
| Indictable Motoring         |          |            |               |
| Suspended Sentence          |          |            |               |
| Other                       |          |            |               |
| Custodial <6 months         |          |            |               |
| Robbery                     |          |            |               |
| Custodial 6 months - <1year |          |            |               |
| Sexual Offences             |          |            |               |
| Custodial 1year - 4 year    |          |            |               |
| Summary Motoring            |          |            |               |
| Custodial 4 year+           |          |            |               |
| Summary Non-Motoring        |          |            |               |
| Indeterminate               |          |            |               |
| Theft and handling          |          |            |               |
| Otherwise Dealt With        |          |            |               |
| Violence Against the Person |          |            |               |
|                             |          |            |               |

Key to the court route splits: MC: those tried and sentenced in the Magistrates Court; MCCC: those who are tried in the Magistrates Court and Sentenced in the Crown Court; CC: combines those defendants who are committed for trial in the Crown Court and sent for trial in the Crown Court into a single category. 

If required, the Courts and Sentencing Module allows trends in the demographic splits and courts and sentencing processes to be implemented when projecting custodial convictions.  This procedure was implemented to create the custodial convictions projections used in the three published scenarios. 

## 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), remand and recall - are modelled using stock-flow structures based on the generic structure shown in Figure C2. The stock-flow structures model the flow of offenders into and out of prison and count the resulting prison population each month. 

Prison Population Average Time Served For the determinate population, the monthly inflows to prison are based on the custodial convictions projections described above. These custodial convictions include offenders that may already be serving a sentence for a previous crime or those who would serve their whole custodial sentence on remand, meaning that they would not be a new reception to prison.  Therefore, to convert from custodial convictions to prison receptions, the historical proportions of custodial receptions to prison receptions for each sub-population are calculated and averaged over the last twelve months of historical data (April 2012 to March 2013 inclusive). Projected receptions are set equal to projected custodial receptions multiplied by the relevant fraction for each sub-population. Monthly outflows for the determinate population are based on observed custodial sentence lengths and the observed percentage of sentence length served taken from January 2012 to March 2013. Each projected offender that enters the model is given a custodial sentence length that is randomly selected from a distribution.  This distribution is populated with custodial sentence lengths from actual offender receptions who share the same characteristics of offence, gender and age group in the observed time period. The per cent of custodial sentence length served is derived in the same manner, except that the observed distribution is made up of discharged offenders and the characteristic of custodial sentence length band is added. Projected prison receptions are sub-divided by an age category, but an exact age of the offender is also applied in the same manner as the custodial sentence lengths.  This allows the model to age the offenders whilst in prison. 

The approach for the other sub-populations is similar and has not been substantially revised since the 2012 publication, with the methodology as follows. For recall prisoners, the model assumes there will be a certain fraction of recall receptions per prison discharge and sets recall receptions in the same month as their related prison discharge. Recall discharged are based on a single average time served variable that is calibrated to fit the actual population over the time period April 2012 to March 2013 We assume that this effectively models the real world situation in which individual prisoners can be recalled a number of times and recall receptions are always some time after their related conviction receptions. For remand prisoners, average custodial sentence lengths are calculated from remand receptions and remand populations and are not calibrated. Instead, reception projections are adjusted so that the modelled stock of prisoners is close to the actual historical numbers. The remand population is generated in two parts both using this approach - untried remand and unsentenced remand populations are generated separately. IPP and life sentence prisoners have an extra section in the stock-flow structure which models their pre-tariff detention. Outflows from this section into the generic stock-flow structure depend on tariff length. Subsequent outflow for IPP and life sentence prisoners depends on the frequency and outcome of Parole Board hearings. The values of these parameters are set at the average of the last 12 months of data (July 2012- June 2013). The non-criminal population is modelled differently. In this case, the projected size of the non-criminal population is set equal to the average size of the noncriminal population over the last two months of available data (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). 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 the Legal Aid, Sentencing and Punishment of Offenders Act which has not yet been realised, the opening of The Verne as an IRC, data recording changes and the assumed impact of changes in court committals.  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 Legal Aid, Sentencing and Punishment of Offenders Act, which achieved Royal Assent in May 2012, has been included as a post model adjustment (where the full impacts have not already been seen within the prison population).  The estimated impacts have been applied to the indeterminate, determinate and remand populations. The Verne is to be opened as an immigration removal centre (IRC) with 580 places in February 2014.  An adjustment has been made to the non-criminal projection for these additional places which would not previously have been counted as part of the prison population.  It is expected that once occupancy meets capacity, The Verne will see more consistency with its occupancy rates in line with the rest of the IRC estate. An adjustment has been made to the remand and sentenced populations for a short-term increase in the population which may be the result of changes to court committals. Data quality work has taken place to improve the recording of offenders who are held post-sentence pending deportation (who should be recorded as noncriminals, but historically around 300 have wrongly remained recorded as sentenced prisoners). An adjustment has been made to the projections to ensure that these offenders are now being included in the non-criminal projections and have been removed from the sentenced population going forward. The other ongoing changes within the system included in previous published projections 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 and seasonality was added back in to the final population projections.  Seasonality was added to the smoothed projections where seasonality was identified using autocorrelation plots.  It was added in to the smoothed projections over the future period using average seasonal adjustments seen in the historical populations. 

## Appendix D: Stakeholders Consulted About Scenarios

Internal stakeholders from across the Ministry of Justice. External representatives from: National Offender Management Service (NOMS)—Estates;  
NOMS—Population Strategy; NOMS—Public Protection Unit; NOMS—Scenario Analysis Team; The Magistrates' Association; The Prison Service; The Probation Service; The National Bench Chairmen's Forum; The Parole Board; The Sentencing Council; 
The Youth Justice Board. 

## Contact Points For Further Information

Current and previous editions of this publication are available for download from www.justice.gov.uk/publications/statistics-and-data/index.htm Press enquiries should be directed to the Ministry of Justice press office, telephone: 020 3334 3536 Other enquiries about these statistics should be directed to: Justice Statistics Analytical Services Ministry of Justice 7th Floor 102 Petty France London SW1H 9AJ General enquiries about the statistical work of the Ministry of Justice can be emailed to: statistics.enquiries@justice.gsi.gov.uk 
 
General information about the official statistics system of the UK is available from www.statistics.gov.uk