This slide pack describes why we’ve changed our method for calculating repeat victimisation on the Crime Survey for England and Wales. It also describes what we have done, and its effect on the estimates we produce.

1. 1
Improving victimisation
estimates from the Crime
Survey for England and
Wales (CSEW)
Joe Traynor
24 January 2019
CSEW survey manager
Centre for Crime and Justice

2. We’ve changed how repeat
victimisation is estimated
• This includes a small change to the survey weights.
• Repeat victimisation is defined as the same thing,
done under the same circumstances, probably by the
same people, against the same victim.
2

3. We’ve replaced the cap of 5 from
the old methodology
• This was a limit on the number of repeat incidents
included in the estimates.
• We’ve replaced this limit with the 98th percentile value.
• We’ve adjusted the weights used on the survey to
better suit the inclusion of these higher counts.
3

4. There has been no impact on the
long-term picture of total crime
• However, the number of incidents for total CSEW
crime are slightly higher across the entire time series
than previously published.
• Since the year to March 2002, the average increase in
total CSEW crime (excluding fraud and computer
misuse) was 2.8%.
4

5. The increase is primarily seen in
violent offences
• Since the year to March 2002 CSEW, estimates of
violence have increased between 6.4% and 31.6%
than previously published. This is due to repeat
incidents being more common in violent offences.
• For most crime types, the estimated number of
incidents is unaffected.
5

6. The number of victims of crime is
almost identical
• The new cap doesn’t impact the number of victims.
• However, the small change to the survey weights had
a marginal effect on all crime survey estimates.
• For example, for the year to March 2018 CSEW, the
estimated number of victims of violent crime increased
by 0.4%.
6

7. Published data
• Estimates using this new methodology are published for
the first time in the Crime in England and Wales: year
ending September 2018 release on 24 January 2019.
• Users should not use releases published before January
2019 for estimates on the number of incidents from the
crime survey.
7

8. 8
Why we’ve changed our
method

9. We interview one adult from
each household selected for
the Crime Survey for England
and Wales (CSEW) sample.
We ask them whether they
have been a victim of any
crime in the last 12 months.
9

10. Measuring incidents of crime
Sometimes a respondent reports being a victim of
multiple crimes that are each isolated incidents differing
in nature. These incidents are counted separately.
10
Fraud
1 incident
+
Theft
1 incident
+
Violence
1 incident
+
Violence 2
1 incident
= 4
incidents

11. Series of incidents
Occasionally, we find people have been victims of the
same thing, done under the same circumstances, probably
by the same people. We call these a series of incidents.
11
Fraud
1 incident
+
Theft
1 incident
+
Violence
1 incident
+
Violence 2
3 incidents
= 6
incidents

12. To gain estimates of the actual amount of crime in
England and Wales, we multiply respondents’ answers by
around 1,300
We survey around 1 in
every 1,300 people
12

13. Total incidents
experienced by
respondent
1 + 1 + 1 + 3 = 6
This respondent
represents 1,300 people so
we multiply their answers
by around 1,300
Fraud: 1 incident
+
Theft: 1 incident
+
Violence A: 1 incident
+
Violence B: 3 incidents
Total incidents counted
1,300 x 6 = 7,800
Weight
Out of around 1,300
adults in the population
we interviewed this adult
in this household.
Incident count Weight x incidents
13

14. Occasionally people report being a victim of a large
number of repeat incidents. The number of such victims
included in the survey, varies from year to year. This can
lead to volatility in the data.
Volatility in the data
14

15. Total incidents
experienced by
respondent
1 + 1 + 1 + 95 = 98
Weight
Out of around 1,300
adults in the population
we interviewed this adult
in this household.
This respondent
represents 1,300 people so
we multiply their answers
by around 1,300
Violence B - 97 incidents
Total incidents counted
1,300 x 98 =
127,400
Fraud: 1 incident
+
Theft: 1 incident
+
Violence A: 1 incident
+
Violence B: 95 incidents
Incident count Weight x incidents
15

16. The number of incidents can change
dramatically between years
This makes it difficult to
determine trends
16

17. When the survey was set up in 1981, it was decided to
cap the number of incidents that can be counted within a
series. This was set at a maximum of 5.
Removing this volatility
17

18. Total incidents
experienced by
respondent
1 + 1 + 1 + 95 = 98
Weight
Out of around 1,300
adults in the population
we interviewed this adult
in this household.
This respondent
represents 1,300 people so
we multiply their answers
by around 1,300
Violence B - 97 incidents
Total incidents counted
1,300 x 98 =
127,400
Fraud: 1 incident
+
Theft: 1 incident
+
Violence A: 1 incident
+
Violence B: 95 incidents
Incident count Weight x incidents
18

19. Total incidents
experienced by
respondent
1 + 1 + 1 + 5 = 8
Weight
Out of around 1,300
adults in the population
we interviewed this adult
in this household.
This respondent
represents 1,300 people so
we multiply their answers
by around 1,300
Violence B - 97 incidents
Total incidents counted
1,300 x 8 =
10,400
Fraud: 1 incident
+
Theft: 1 incident
+
Violence A: 1 incident
+
Violence B: 5 offences
Incident count with cap Weight x incidents
19

20. Capping the number of incidents
reduces volatility
This makes it possible
to discern trends over
time
20

21. However…
• We now know that the arbitrary cap of 5 disregards a
lot of incidents, especially acts of violence.
• Victims of violence are more likely to be repeat victims.
21

22. 22
0
20
40
60
80
100
Violence Theft Offences Criminal damage Robbery
Percentageofincidents
INCLUDED EXCLUDED
40% of violent
incidents were
excluded in this
CSEW survey
year compared
to only 9% of
theft offences.
Proportion of CSEW incidents excluded by crime type,
example taken from the year ending March 2017

23. 23
between handling volatility in the estimates and not
disregarding a lot of incidents
A balance was needed

24. To find this balance we…
• commissioned an independent review
• ran a public consultation
• sought advice from the National Statistician’s Crime
Statistics Advisory Committee
• published our decisions in response to the consultation
in November 2016
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25. We decided to…
• remove the arbitrary limit of 5
• move to the 98th percentile value where this value is
greater than 5
• adjust the weights used on the survey to better suit the
inclusion of these higher counts
• publish the uncapped data with caveats to their use as
they are subject to considerable volatility
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26. Calculating the 98th percentile
• Order the victims (across 3 years) by the number of
repeat incidents they have experienced.
• Find the victim who is at the 98th percentile, that is,
below which 98% of victims are found.
• Use the number of repeat incidents experienced by
that victim.
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27. 27
We now include a much higher volume of violent incidents
reported by respondents
What does this mean in
practice?

28. 28
0 10 20 30 40 50
Jan '95 to
Dec '95
Apr '07 to
Mar '08
Apr '16 to
Mar '17
Apr '17 to
Mar '18
Percentage of incidents
Proportion excluded
with 98th percentile
Proportion excluded
with Cap of 5
Proportion of violent incidents excluded by methodology for a
selection of survey years

29. The overall picture hasn’t changed, the number of
incidents has increased across the whole series
What’s the impact on
total crime?
29

30. 30
0
5,000
10,000
15,000
20,000
Jan '81
to Dec
'81
Jan '87
to Dec
'87
Jan '93
to Dec
'93
Jan '97
to Dec
'97
Apr '01
to Mar
'02
Apr '03
to Mar
'04
Apr '05
to Mar
'06
Apr '07
to Mar
'08
Apr '09
to Mar
'10
Apr '11
to Mar
'12
Apr '13
to Mar
'14
Apr '15
to Mar
'16
Apr '17
to Mar
'18
Numberofincidents(thousands)
Capped at 5
98th percentile
Total CSEW crime excluding fraud and computer misuse by old
and new methodology, year ending December 1981 to year
ending March 2018

31. The overall picture is broadly similar, the number of
incidents has increased across the whole series
What is the impact on
violent crime?
31

32. 32
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
4,500
5,000
Jan '81
to Dec
'81
Jan '87
to Dec
'87
Jan '93
to Dec
'93
Jan '97
to Dec
'97
Apr '01
to Mar
'02
Apr '03
to Mar
'04
Apr '05
to Mar
'06
Apr '07
to Mar
'08
Apr '09
to Mar
'10
Apr '11
to Mar
'12
Apr '13
to Mar
'14
Apr '15
to Mar
'16
Apr '17
to Mar
'18
Numberofincidents(thousands)
Capped at 5
98th percentile
This rise in violence that we see here
is a genuine reflection of sustained
higher volumes of repeat incidents
Being reported by respondents
around this time-period.
Across financial years, new violence estimates will be between
6% to 32% higher than previously published estimates

33. What’s next
• We plan to publish microdata containing:
• new crime category variables based on the 98th percentile
• new crime category variables with the removal of the cap
altogether for specialist users to conduct their own
analyses
• We are also planning a new strand of research on the
extent and characteristics of repeat victimisation.
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34. In summary: how have we changed the way we treat CSEW
data back to 1981?
For some crimes
where repeat
victimisation
appears more
frequently in the
untreated data, the
cap of 5 was too
stringent.
We have decided
to use the 98th
percentile count
for each of these
crime types
instead.
No change
Maximum number of
incidents in a series
remains at 5 where
98th percentile is
below this level.
Otherwise maximum
number of incidents
reflects the 98th
percentile count of
number of incidents
for that crime type.
• Burglary
• Other Household Theft
• Personal Theft Offences
• Vehicle Crime
• Bicycle Theft
• Robbery
• Fraud
• Computer Misuse
Violence
New maximum values
from 1981 to 2018
range between 8 - 20.
Criminal damage
For some years between
1981 and 2018 a maximum
value of 9 will be applied.
Weights
The inclusion of
more count data
from violence
has meant that
we have had to
pay more
attention to the
impact of
extreme
weights and
alter they way in
which we treat
these cases.
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