How the measure of proven re-offending has changed and the effect of these changes
Source: data.gov.uk (2018-05-25)

Proven Re-offending statistics. Key statistics on proven reoffending in England and Wales. It gives proven reoffending figures for offenders who were released from custody, received a non-custodial conviction at court, or received a caution or reprimand.

How the measure of proven re-offending has 
changed and the effect of these changes 
 
 
 
 
 
 
 
 
 
 
Ministry of Justice 
Statistics Bulletin 
 
 
 
30 January 2014 

 
How the measure of proven re-offending has changed 
and the effect of these changes 
 
Background 
 
The MoJ launched a statistical consultation on improvements to the 
transparency and accessibility of our information in 2010 and a response to 
the consultation was published in March 20111. One aspect of the 
consultation was the measurement of proven re-offending. 
                                                
 
Prior to the consultation there were six different measures of proven re-
offending: 
 
 National adult proven re-offending; 
 
 Local adult proven re-offending; 
 
 National youth proven re-offending; 
 
 Local youth proven re-offending; 
 
 Prolific and other priority offending (PPO); and 
 
 Drug-misusing proven offending. 
 
The new approach to measuring proven re-offending integrates these 
approaches into a single framework. This allows users to: 
 
 form a clear picture of proven re-offending at national and local levels; 
 
 compare adult and youth results, and enable other work on transition 
between the youth and adult criminal justice systems; 
 
 understand how results for different offender groups (such as those 
managed by the prison and probation services, those under the PPO 
schemes, drug-misusing offenders, first time entrants, etc.) fit in to the 
overall picture on proven re-offending; and 
 
 continue to analyse proven re-offending behaviour for particular types 
of offender. 
 
 
1 The response to the consultation is available here: 
webarchive.nationalarchives.gov.uk/20111121205348/http:/www.justice.gov.uk/consultations/
565.htm 
 
2

 
Comparing trends in re-offending 
 
Table 1 shows the proportion of offenders with a proven re-offence/re-
conviction using the new measure of re-offending and the previous measures 
of adult re-conviction and juvenile re-offending. Comparisons we make use 
cohorts up to 2009. 
 
Re-offending rates are lower using the new measure than using the previous 
measure. The differences are as follows: 
 
 For adult and juvenile offenders the new measure is based on all 
offenders released from custody, receiving a non-custodial conviction 
at court, a caution, reprimand, warning or tested positive for opiates or 
cocaine over a 12 month period, but the previous measures only 
included offenders released from custody or commencing a court order 
in the first three months of the year. Using a three month sample over-
represents prolific offenders in comparison to a full year’s worth of data. 
 
 For adults the new measure counts all offenders including those who 
received a caution, fine or discharge, where the previous adult 
measure only included those who commenced a court order or who 
were discharged from custody. 
 
 For adult offenders, the new measure is a measure of proven re-
offending (which counts offences proven through a court conviction or a 
caution) whereas the previous measure is a measure of re-conviction 
(which only counts offences proven through a court conviction). 
 
As a result, re-offending rates are 14.4 percentage points lower for adults and 
rates for juveniles are 4.1 percentage points lower using the new measure. 
 
However, the re-offending rates are similar for adults given a court order or 
who received a custodial sentence, including those given a sentence of less 
than 12 months. Rates are between 1.0 and 2.6 percentage points lower 
using the new measure. 
 
Table 1: Re-offending using the new and previous measures, 2009 
 
New measure 
Previous measure(s)
Adults
24.9
39.3
Juveniles
32.8
36.9
Adults given a court order
34.5
35.5
Adults given a custodial sentence
46.8
48.5
Adults given a custodial sentence of less than 12m
56.8
59.4
 
 
Figure B1 shows re-offending rates for adult offenders between 2000 and 
2009 using the new and previous measure. 
 
For 2009, 24.9% of adult offenders have a proven re-offence within 12 months 
using the new measure compared to 39.3% using the previous re-conviction 
 
3

 
measure. However, trends for adult offenders are similar using the two 
measures. The proportion of offenders with a proven re-offence/re-conviction 
rose between 2000 and 2002, fell between 2002 and 2006, rose between 
2006 and 2008, and fell between 2008 and 2009 using both measures. 
 
Figure B1: Adult re-conviction/re-offending, by re-offending measure, 
2000, 2002 to 2009 
 
27.6%
26.9%
25.5%
24.9%
24.6%
24.8%
25.4%
24.9%
43.0%
45.4%
42.9%
41.2%
38.6%
39.0%
40.1%
39.3%
26.2%
45.5%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
50%
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
Year
Re-conviction/re-offending rates 
New Measure
Old measure
Data not available
 
The overall reduction in re-offending is smaller using the new measure (1.2 
percentage points between 2000 and 2009 and 0.5 percentage points 
between 2008 and 2009) than using the previous measure (3.7 percentage 
points between 2000 and 2009 and 0.8 percentage points between 2008 and 
2009). 
 
Figure B2 shows re-offending rates for juvenile offenders between 2000 and 
2009 using the new and previous measure. 
 
In 2009, 32.8% of young offenders re-offended within 12 months using the 
new measure compared to 36.9% using the previous measure. The reduction 
in re-offending is smaller using the new measure (0.9 percentage points 
between 2000 and 2009 and 0.1 percentage points between 2008 and 2009) 
than using the previous measure (3.3 percentage points between 2000 and 
2009 and 0.4 percentage points between 2008 and 2009). Overall, the trends 
are broadly similar. 
 
 
4

 
Figure B2: Juvenile re-offending, by re-offending measure, 2000, 2002 to 
2009 
 
33.7%
33.4%
34.3%
33.6%
33.6%
33.9%
32.5%
32.9%
32.8%
40.2%
38.5%
39.0%
38.6%
38.4%
38.7%
37.5%
37.3%
36.9%
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
Year
Re-offending rates 
New Measure
Old measure
Data not available
 
 
Trends in proven re-offending/re-conviction rates for adult custodial offenders 
are similar using the new and previous measures. The proportion of offenders 
given a custodial sentence of less than 12 months who re-offended rose 
between 2000 and 2009 using both measures (by 2.6 percentage points using 
the new measure and 1.4 percentage points using the previous measure). 
The proportion of offenders given any custodial sentence who re-offended fell 
between 2000 and 2009 using both measures (by 2.6 percentage points using 
the new measure and 2.9 percentage points using the previous measure). 
 
5

 
 
6
Figure B3: Adult re-conviction/re-offending of custodial offenders, by re-
offending measure and sentence, 2000 and 2009 
 
54.3%
58.0%
49.4%
51.4%
56.8%
59.4%
46.8%
48.5%
0%
10%
20%
30%
40%
50%
60%
70%
New measure <12m
Previous measure
<12m
New measure (all
sentence lengths)
Previous measure all
sentence lengths)
Disposal 
Re-offending/re-conviction rates
2000
2009
 
 
The change in methodology 
 
The following sections provide detail regarding the change in methodology 
between the methods in measuring re-offending and how those changes 
impact on the data. 
 
The table below provides a comparison of the previous methodologies with 
the new approach.

 
Table 2: Re-offending using the new and previous measures 
 
Comparison of previous and new measures of proven re-offending 
 
Previous measures of re-offending 
New measure of re-
offending 
 
National adult 
re-conviction 
Local adult re-
offending 
National youth re-
offending 
Local youth re-
offending 
Prolific and other 
Priority Offending 
(PPO) 
Drug-misusing 
offending 
The cohort 
Offenders aged 
18+ discharged 
from custody or 
commencing 
court orders 
under probation 
supervision 
between January 
to March 
Offenders 
aged 18+ on 
the probation 
caseload at the 
end of each 
calendar 
quarter 
Offenders aged 10-
17 discharged from 
custody, receiving a 
court conviction or 
receiving a 
caution/reprimand or 
final warning between 
January and March 
Offenders aged 
10-17 discharged 
from custody, 
receiving a court 
conviction or 
receiving a 
caution/reprimand 
or final warning 
between January 
and March 
All offenders 
identified as being 
on the PPO 
scheme as at 1 
April 
All Class A drug 
offenders 
identified 
through positive 
drug tests on 
arrest, OASyS 
or drug 
requirement as 
part of a court 
order, CJIT 
identification, or 
identification on 
prison release 
between 
January and 
March 
All offenders who 
received a 
caution/reprimand or 
warning, were 
convicted at court 
(other than custody), 
were discharged 
from custody, or 
tested positive for 
cocaine or opiates 
on arrest over a 12 
month period. 
The follow-up 
period to 
measure re-
offending 
12 months for 
offences to occur 
and a further 6 
months for 
offences to be 
proved 
3 months for 
offences to 
occur and a 
further 3 
months for 
offences to be 
proved 
12 months for 
offences to occur and 
a further 6 months for 
offences to be proved 
12 months for 
offences to occur 
and a further 3 
months for 
offences to be 
proved 
12 months for 
offences to occur 
and a further 3 
months for 
offences to be 
proved 
12 months for 
offences to 
occur and a 
further 3 
months for 
offences to be 
proved 
12 months for 
offences to occur 
and a further 6 
months for offences 
to be proved 
 
7 

 
Comparison of previous and new measures of proven re-offending 
 
Previous measures of re-offending 
New measure of re-
offending 
 
Local adult re-
offending 
National youth re-
offending 
Local youth re-
offending 
Drug-misusing 
offending 
National adult 
re-conviction 
Prolific and other 
Priority Offending 
(PPO) 
The headline 
measure 
Frequency of re-
offending (the 
number of proven 
re-offences per 
100 offenders) 
Proportion of 
offenders re-
offending, 
compared to 
the rate that 
would be 
expected 
based on the 
offender 
characteristics 
Frequency of re-
offending (the 
number of proven re-
offences per 100 
offenders) 
Frequency of re-
offending (the 
number of proven 
re-offences per 
100 offenders) 
Number of further 
offences compared 
to number in 
previous year, 
against the 
reduction that 
would be expected 
given time on the 
PPO scheme 
Number of 
further offences 
compared to 
what would be 
expected based 
on their 
previous 
offending 
history 
Proportion of 
offenders re-
offending 
We also include 
information on the 
frequency of re-
offending and 
information on the 
predicted rate based 
on offender 
characteristics 
What counts as 
a proven re-
offence 
Offences 
committed within 
the follow-up 
period which 
were proved by a 
court conviction 
either within the 
follow-up period 
or in a further six 
months 
Offences 
committed 
within the 
follow-up 
period which 
were proved by 
a court 
conviction or 
caution either 
within the 
follow-up 
period or in a 
further three 
months 
Offences committed 
within the follow-up 
period which were 
proved by a court 
conviction or 
reprimand or final 
warning either within 
the follow-up period 
or in a further six 
months 
Offences 
committed within 
the follow-up 
period which 
were proved by a 
court conviction 
or reprimand or 
final warning 
either within the 
follow-up period 
or in a further 
three months 
Offences 
committed within 
the follow-up period 
which were proved 
by a court 
conviction or 
caution either 
within the follow-up 
period or in a 
further three 
months. Breach 
offences that lead 
to substantive 
recorded 
convictions are 
included 
Offences 
committed 
within the 
follow-up period 
which were 
proved by a 
court conviction 
either within the 
follow-up period 
or in a further 
three months 
Offences committed 
within the follow-up 
period which were 
proved by a court 
conviction or 
caution/reprimand or 
warning either within 
the follow-up period 
or in a further six 
months 
 
8 

 
 
9 
Comparison of previous and new measures of proven re-offending 
 
Previous measures of re-offending 
 
Local adult re-
offending 
National youth re-
offending 
Local youth re-
offending 
Drug-misusing 
offending 
National adult 
re-conviction 
Prolific and other 
Priority Offending 
(PPO) 
New measure of re-
offending 
A predicted rate 
of re-offending 
was included for 
the proportion of 
offenders 
expected to re-
offend based on 
their 
characteristics 
A predicted rate 
of re-offending 
was included for 
the proportion of 
offenders 
expected to re-
offend based on 
their 
characteristics 
A predicted rate of 
re-offending was 
included for the 
proportion of 
offenders expected 
to re-offend based 
on their 
characteristics 
 
Use of a 
predicted rate 
Logistic 
regression was 
used 
Logistic 
regression was 
used 
Logistic regression 
was used 
No predicted rate 
Evidence on the 
link between time 
on the PPO 
scheme and 
expected 
reductions in 
further offending 
were used to 
assess reductions 
in number of 
offences compared 
to the previous year
A predicted rate 
of re-offending 
was included for 
the proportion 
of offenders 
expected to re-
offend based on 
their previous 
criminal history 
Response 
surface 
methodology 
was used 
A predicted rate of 
re-offending is 
included for the 
proportion of 
offenders expected 
to re-offend based 
on their 
characteristics 
Logistic regression is 
used 
Data source 
Police National 
Computer 
Police National 
Computer 
Police National 
Computer 
Youth Offending 
Teams data 
Police National 
Computer 
Police National 
Computer 
Police National 
Computer 
Geographic 
breakdown 
None 
Region, 
Probation area, 
Local Authority 
None 
Youth Offending 
Team level 
Police Force and 
Local Authority 
level 
Drug Action 
team and Local 
Authority level 
Upper and lower tier 
local authority areas 
for all offenders. 
Other breakdowns 
for specific 
categories of 
offender. 
 

 
The effect of the changes 
 
Adults 
 
Differences in methodology are reflected in different results. Table 3 shows 
the impact on reported rates of adult re-conviction/re-offending. The table 
breaks down the changes between the previous measure and the new 
measure to identify the different effects of the changes in methodology. 
 
Table 3: Re-offending/re-convictions data for adult offenders, 2000, 2002 
to 2009 
 
Previous1 measure: re-
convictions (prison and 
probation offenders only), 
first quarter of the year
Previous measure: re-
convictions (prison and 
probation offenders only), 
whole year
New measure: re-
offending (prison and 
probation offenders only), 
whole year
New measure: proven re-
offending (all offenders), 
whole year
2000
43.0
40.0
40.9
26.2
2002
45.5
42.0
43.0
27.6
2003
45.4
41.5
42.4
26.9
2004
42.9
38.6
39.8
25.5
2005
41.2
36.6
38.4
24.9
2006
38.6
35.6
37.6
24.6
2007
39.0
35.9
37.9
24.8
2008
40.1
36.1
37.9
25.4
2009
39.3
34.7
36.2
24.9
2000
1.85
1.66
1.69
0.89
2002
2.13
1.84
1.87
0.99
2003
2.05
1.73
1.76
0.93
2004
1.81
1.51
1.54
0.83
2005
1.66
1.36
1.40
0.77
2006
1.44
1.26
1.31
0.73
2007
1.47
1.27
1.32
0.73
2008
1.55
1.27
1.31
0.75
2009
1.41
1.15
1.18
0.70
2000
4.30
4.15
4.13
3.39
2002
4.68
4.39
4.36
3.59
2003
4.52
4.18
4.15
3.44
2004
4.23
3.91
3.87
3.27
2005
4.03
3.70
3.65
3.10
2006
3.73
3.54
3.48
2.95
2007
3.78
3.53
3.48
2.94
2008
3.88
3.51
3.46
2.93
2009
3.57
3.31
3.27
2.80
2000
42,734
148,052
148,052
477,698
2002
43,247
157,243
157,243
495,664
2003
44,095
159,686
159,686
520,660
2004
46,532
163,775
163,775
512,600
2005
43,429
170,021
170,021
532,045
2006
50,281
181,726
181,726
571,458
2007
50,085
190,418
190,418
595,020
2008
53,718
197,035
197,035
589,948
2009
56,616
200,077
200,077
576,255
1. Based on the national adult re-convictions publication (March 2011)
Proportion 
Frequency (average per offender)
Frequency of re-offenders (average per re-offender)
Number of offenders
 
 
Among adult offenders in 2009, the previous national measure (the first 
column) shows that 39.3% of adult offenders were re-convicted within a year 
based on a sample of 56,616 offenders. 
 
 
 
10

 
The second column shows the re-conviction rates from the previous measure 
looking at offenders who were released from custody or commenced a court 
order, but at any point during the year. The inclusion of offenders from a full 
12 month period means the results are calculated using the full proven 
offender population rather than a sample – this ensures we do not over-
represent prolific offenders in the cohort, which is a problem in using a 
January to March sample as in the previous adult re-conviction measure. 
 
This leads to a lower proportion of re-convicted offenders (between three and 
five percentage points, e.g. 34.7% compared to 39.3% in 2009). The change 
to a full year also increases the number of offenders, to 200,077 in 20092. 
 
The third column shows the proven re-offending rates from the new measure, 
but still based only on those offenders who were released from custody or 
commenced a court order at any point during the year. Proven re-offending 
includes offences which result in a caution in addition to those resulting in a 
conviction at court. The proportion of offenders who were proven to re-offend 
is between one and two percentage points higher than for those who were re-
convicted (36.2% compared to 34.7% in 2009). There is little difference at this 
stage because we are still only considering offenders who already have a 
prison or a court order. 
 
The fourth column shows the re-offending rates from the new measure 
looking at all adult offenders who received a caution, a conviction at court, 
discharged from custody, or tested positive for cocaine or opiates. The 
inclusion of these offenders increases the numbers considerably. In 2009, the 
previous adult measure tracks the re-offending behaviour of 56,616 offenders; 
the new measure tracks 576,255 offenders. The inclusion of offenders who 
received less severe disposals and are generally less prolific in nature 
reduces the proportion who re-offend by around 11 to 16 percentage points 
(36.2% compared to 24.9% in 2009). 
 
Change over time 
 
Compared to the previous measure, the reduction over time in the proportion 
of offenders who re-offend is much lower using the new measure. Using the 
previous measure, between 2000 and 2009, the proportion of offenders who 
were re-convicted fell 3.7 percentage points (from 43.0 to 39.3%). Using the 
new measure, the proportion of offenders who committed a proven re-offence 
fell 1.2 percentage points (from 26.2 to 24.9%). 
 
 
                                                 
2 The previous measure includes offenders released from custody or who commenced a court 
order in the first three months of the year, shown in column one. Column two includes 
offenders released from custody or who commenced a court order in the 12 month period. 
The number of offenders shown in column two is less than four times as many as in column 
one. This is because some offenders commence a court order or are discharged from custody 
more than once in a year. These calculations only count each offender once e.g. offender Y is 
discharged from custody in the first quarter of the year, and discharged again in the second 
quarter, but he is only counted as a single offender 
 
 
 
11

 
Juveniles
 The only change between the previous measure and the new measure of re-
offending among young people is the move from a one quarter sample to 
including all young offenders over the period of a year. 
 
Table 4: Re-offending data for juvenile offenders, 2000, 2002 to 2009 
 
Previous measure1             
proven re-offending
New measure proven re-
offending 
2000
40.2
33.7
2002
38.5
33.4
2003
39.0
34.3
2004
38.6
33.6
2005
38.4
33.6
2006
38.7
33.9
2007
37.5
32.5
2008
37.3
32.9
2009
36.9
32.8
2000
1.51
1.12
2002
1.42
1.10
2003
1.42
1.09
2004
1.32
1.03
2005
1.25
0.98
2006
1.23
0.97
2007
1.16
0.90
2008
1.14
0.91
2009
1.10
0.90
2000
3.77
3.32
2002
3.69
3.29
2003
3.63
3.19
2004
3.43
3.06
2005
3.26
2.91
2006
3.18
2.86
2007
3.08
2.77
2008
3.06
2.75
2009
2.99
2.75
2000
41,176
139,326
2002
40,753
136,401
2003
40,297
138,379
2004
44,153
149,452
2005
45,337
163,545
2006
48,938
171,061
2007
52,544
171,454
2008
44,837
145,579
2009
37,472
121,107
1. Based on the national juvenile re-offending publication (March 2011)
publication
Proportion 
Number of offenders
Frequency (average per offender)
Frequency of re-offenders (average per re-offender)
 
 
As for adults, using the whole year reduces the proportion of offenders who 
re-offended because we do not over-represent prolific offenders in the cohort, 
which is a problem in using a January to March sample. Table 4 shows the 
reduction is between four and seven percentage points.  
For 2009, with the previous measure, 36.9% commit a proven re-offence 
within one year; with the new measure, 32.8% do so. The new measure, 
 
 
 
12

 
which is based on offenders from a 12 month period, includes over three 
times as many offenders as the existing measure. 
 
Change over time 
 
Compared to the previous measure, the reduction in the proportion of 
offenders who re-offend between 2000 and 2009 is much lower using the new 
measure. 
 
Using the previous measure, between 2000 and 2009, the proportion of 
offenders who were proven to re-offend fell 3.3 percentage points (from 40.2 
to 36.9%). Using the new measure, the proportion of offenders who 
committed a proven re-offence fell 0.9 percentage points (from 33.7 to 
32.8%). 
 
Drug-misusing offenders 
 
Published results for drug-misusing offenders on the previous measure 
covered 2008 and 2009; results using the new measure cover from 2004 
onwards. 
 
The previous measure: 
 
 Includes offenders who have been identified in the first quarter of the 
year, whereas the new measure includes offenders from any point 
during the year. 
 
 Includes all drug-misusing offenders irrespective of the date of proven 
offence, whereas the new measure includes identified drug-misusing 
offenders who have received a caution, been convicted at court, been 
discharged from custody, or tested positive for cocaine or opiates on 
arrest during a 12 month period. 
 
 Counts re-offences that were proven through a court conviction, 
whereas the new measure counts re-offences that were proven by a 
court conviction or caution. 
 
As for adult and juvenile offenders, using the whole year to identify offenders 
reduces the proportion of offenders who re-offend, because we do not over-
represent prolific offenders in the cohort, which is a problem in using a 
January to March sample. Table 5 shows the impact on reported rates of re-
offending/re-conviction by drug-misusing offenders. 
 
 
 
13

 
Table 5: Re-offending data for drug-misusing offenders, 2004 to 2009 
 
 
Previous measure1 proven re-
conviction
New measure of proven re-
offending 
2004
67.3
2005
65.3
2006
58.6
2007
57.2
2008
61.0
56.4
2009
57.0
54.7
2004
3.20
2005
2.94
2006
2.37
2007
2.34
2008
2.6
2.29
2009
2.2
2.10
2004
4.75
2005
4.51
2006
4.03
2007
4.09
2008
4.3
4.06
2009
3.9
3.84
2004
20,652
2005
29,112
2006
44,597
2007
54,474
2008
20,934
59,039
2009
20,109
53,109
1. Based on the national drug-misusing offenders publication 
(December 2010)
Proportion 
Number of offenders
Frequency of re-offenders (average per re-offender)
Frequency (average per offender)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Table 5 shows that the proportion of offenders who commit a proven re-
offence is between two and five percentage points lower using the new 
measure (57.0% using the previous measure compared to 54.7% using the 
new measure). The new measure, which follows offenders over a 12 month 
period, includes between two and three times as many offenders as the 
existing measure. 
 
Prolific and other priority offenders 
 
Published results for prolific and other priority offenders (PPOs) on the 
previous measure presented the frequency of proven re-offending for all 
PPOs; results using the new measure cover the proportion of offenders 
proven to re-offend, and the frequency of proven re-offending for all offenders 
and for re-offenders from 2005 onwards. 
 
 
 
 
14

 
The previous measure: 
 
 Includes offenders who have been identified in the first quarter of the 
year, whereas the new measure includes offenders from any point 
during the year. However, PPOs are generally on the PPO programme 
for a sustained period of time so this only has a moderate impact on 
numbers of offenders included. 
 
 Includes all identified PPOs, whereas the new measure includes 
identified PPOs who have tested positive for cocaine or opiates, 
received a caution, been convicted at court, or been discharged from 
custody during a 12 month period. 
 
 Counts re-offences that are proven through a court conviction or 
caution and also includes breach offences that lead to substantive 
recorded convictions. The new measure only includes re-offences 
proven through a court conviction or caution. 
 
Table 6 shows the impact on reported rates of proven re-offending by PPOs 
and on numbers of offenders included in the measure. 
 
Table 6: Re-offending data for Prolific and other Priority Offenders, 2005 
to 2009 
 
Previous  measure1 proven re-
offending
New measure of proven re-
offending 
2005
77.0
2006
75.7
2007
75.8
2008
77.2
2009
56.0
75.1
2005
4.01
2006
3.83
2007
3.80
2008
2.6
3.80
2009
2.4
3.49
2005
5.21
2006
5.06
2007
5.01
2008
4.93
2009
4.3
4.65
2005
8,555
2006
8,239
2007
8,309
2008
10,771
8,607
2009
10,635
8,156
1. Based on the national Prolific and other Priority Offenders publication
(March 2010)
Proportion 
Frequency (average per offender)
Frequency of re-offenders (average per re-offender)
Number of offenders
 
 
 
 
 
15

 
The average number of proven re-offences committed by PPOs in 2009 is 
lower for the previous measure than for the new measure in 2008 (2.4 re-
offences per offender using the previous measure, but 3.49 using the new). 
 
The previous measure includes PPOs who have not been proven guilty of an 
offence or been discharged from custody in the 12 month period when the re-
offending cohort is formed. This type of offender is likely to have a lower level 
of re-offending. 
 
These differences may help to explain: 
 
 why the frequency of re-offending is lower for the previous measure 
than for the new measure in 2009 (2.4 re-offences per offender using 
the previous measure, but 3.49 using the new); and 
 
 why the previous measure includes nearly 2,500 more PPOs in 2009 
than does the new measure. 
 
Local adult re-offending 
 
The most similar results for the new measure of re-offending and the existing 
local measure of adult re-offending are the early estimates of re-offending of 
offenders given a court order. Like the existing measure of local adult re-
offending, the early estimates of offenders given a court order: 
 
 measure re-offending over three months; 
 
 only measures offenders under probation supervision; 
 
 provides results by probation trust; and 
 
 compares actual re-offending rates with a predicted re-offending rate. 
 
There remain significant differences between the early estimates and the 
existing local adult measure of re-offending, including: 
 
 The existing local adult measure includes offenders on licence – the 
early estimates include offenders commencing court orders only; 
 
 The existing local adult measure uses a ‘snapshot’ approach. This 
means offenders are counted if they are on the caseload at certain 
times in the year. Offenders who are on the caseload for a short period 
of time may not get counted with the existing measure. The early 
estimates count every offender who commences a court order; 
 
 Because the existing local adult measure uses a ‘snapshot’ approach 
some offenders may get counted up to four times if they are on the 
caseload for over 12 months. The early estimates count every offender 
once; 
 
 
 
 
16

 
 The existing local adult measure measures the re-offending of 
offenders at any point during the court order – the early estimates 
measure re-offending in the first three months after an offender 
commenced a court order; and 
 
 The predicted score for the existing local adult measure was derived 
from analysis of 2007 re-offending data and the prediction for the early 
estimates was derived from analysis of 2008 re-offending data. 
 
These differences explain why the re-offending rate is higher with the early 
estimates of re-offending by offenders commencing a court order than with 
the existing measure of local adult re-offending: 
 
 offenders on licence have lower rates of re-offending than those 
commencing a court order; and 
 
 offenders serving a court order have lower rates of re-offending the 
longer they are on that court order. 
 
However, the prediction for the early estimates has been tailored specifically 
to the relevant group of offenders. 
 
Local youth re-offending 
 
The previous measure of youth re-offending used data that Youth Offending 
Teams (YOT) collected themselves from their local police and courts. The 
measure was used as management information and was never published or 
put into the public domain. The new measure uses data from the Police 
National Computer (PNC). Internal analysis and discussion with stakeholders 
has highlighted a number of differences between the two data sources: 
 
 The PNC includes a number of offenders who have received a 
reprimand or final warning which do not always appear on the YOT 
systems. As a result, there are more youth offenders and a higher 
overall youth re-offending rate using the new measure than using the 
previous local youth re-offending measure. 
 
 The PNC includes more comprehensive data on re-offending as adults 
by offenders who originally offended as youths. 
 
 Using PNC data reduces the data-collection burden on YOT and local 
police forces. 
 
 PNC data measures re-offending on recordable offences and YOT data 
measures re-offending on all offences. Offences which are not 
recordable include speeding offences, parking offences and other 
minor motoring offences. As a result, YOT data is more comprehensive 
for motoring re-offences. 
 
 
 
 
17

 
 The new measure allocates offenders to a locality using their home 
address data from the PNC; the previous local youth measure 
allocated offenders using offender management data. As a result, 
Looked After Children (LAC) who are in foster care, or in a children’s 
home, or in a boarding school or live with another adult known to 
children’s services, maybe allocated to a different YOT under the 
previous youth measure than the new measure. 
 
 For their re-offending to be included in the new measure, administrative 
data on young people in custody and secure accommodation has to be 
matched to the PNC. Some cases are not successfully matched. This 
process was not required for these offenders to be included in the 
previous local youth measure. As a result, YOT data can be more 
comprehensive regarding custodial offenders or those in secure 
accommodation. 
 
 Using PNC data provides an external measure of youth re-offending, 
which makes it an appropriate data-source to support any future 
policies which tie local funding to re-offending performance. 
 
 Using PNC data allows local youth re-offending to be measured on the 
same basis as national youth re-offending and adult re-offending, 
permitting adult and youth re-offending to be measured on a like-for-
like basis and a more comprehensive picture of re-offending to be 
formed. 
 
Work is underway to fully quantify the extent of these differences. 
 
 
 
18

 
 
 
 
19
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Ministry of Justice 
Justice Statistics Analytical Services 
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is available from www.statistics.gov.uk. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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