5. Bringing together crime statistics
Why are there two sources of crime statistics?
This chapter compares police recorded crime and the SCJS to help assess the scale of the difference between the volume of crime that is recorded by the police, and the level of crime that is estimated by the survey to be experienced by the adult population in Scottish households. It builds on an analytical paper, published in 2014 and uses a subset of comparable crime to compare SCJS estimates with police recorded crime figures.
A range of information is provided based on analysis of this comparable subset of crime. The two sources of crime statistics are reviewed briefly first, then the chapter looks at trends in these two sources over time and trends in three broadly comparable sub-groups over time (violent crime, acquisitive crime and vandalism). Finally this chapter compares police recorded crime with the proportion of SCJS crime estimated to have been reported to the police.
The SCJS and police recorded crime are essential, complementary evidence sources that, together, present a fuller picture of crime in Scotland
Crimes recorded by the police provide information on crimes that the police face and are important because they can help to evaluate measures in place to reduce crime, assess the performance of policing and criminal justice organisations and also allow them to use evidence to adequately target resources. However, crime recording is sensitive to changes in public reporting practices, police recording practices and, in part, police deployment and activity. In addition, not all crimes come to the attention of the police.
Crime surveys allow a wider assessment of the overall level of crime and likelihood of experiencing crime and provide a range of additional information, for example on the characteristics of crime, the relative likelihood of experiencing crime across the population and on repeat victimisation. However surveys are often not as good at picking up some rarer crimes, crimes where there is no specific victim or where the victim is not covered by the survey sample; for example, crimes against businesses and children.
In summary, the SCJS and police recorded crime cover different crime and offence groups, different populations and also different timescales. The 2017/18 Recorded Crime results cover crimes recorded in the financial year 2017/18; the 2017/18 SCJS includes crimes experienced by SCJS respondents over a 25-month ‘recall period’. They each feature relative strengths and limitations, making them more appropriate in different contexts and for different purposes.
Taking account of these differences, comparisons between recorded crime and SCJS data can be made by examining a broadly comparable subset of crimes which are covered by each source, and can be coded in the survey in approximately the same way as they would be recorded by the police. Almost two-thirds (64%) of ‘all SCJS crime’ as measured by the 2017/18 SCJS falls into categories that can be compared with crimes recorded by the police.
What are the trends in comparable SCJS and police recorded crime?
There is relatively good consistency in the trends in overall comparable SCJS and police recorded crime, particularly over the longer term with both showing large decreases.
Of the 602,000 crimes overall estimated by the 2017/18 SCJS, almost two-thirds (386,000) can be compared with police recorded crimes. Figure 5.1 demonstrates the scale of the difference between the two series of crime statistics. In 2017/18, the police recorded 130,418 crimes and offences in the comparable subset, representing 34% of the number of crimes in the SCJS comparable subset (Table 5.1 below).
There are a number of reasons for these differences, including that SCJS estimates tend to be higher than recorded crime figures, even in the comparable category, because the survey is able to capture crime which does not come to the attention of the police. Overall the 2017/18 SCJS estimates that 40% of all crime in the comparable subset came to the attention of the police.
Figure 5.1: Comparable recorded crime and SCJS estimates, 2008/09 to 2017/18
Sources: SCJS, Police recorded crime.
At an overall level, both the SCJS and police recorded crime provide evidence of large decreases in crime in Scotland over the last decade. As shown in the table, SCJS comparable crime fell by 47% between 2008/09 and 2017/18, whilst comparable recorded crime is down by 40% over the same period. Since 2016/17, the SCJS found no change in the level of comparable crime, whilst comparable recorded crime fell by 1%. It is notable that Her Majesty’s Inspectorate of Constabulary in Scotland (HMICS)’s auditing of incidents and crimes recorded by Police Scotland indicates that police compliance in recording is generally good overall.
Table 5.1: Comparable crime group estimates, 2008/09 to 2017/18
|2008/09||2016/17||2017/18||% change since 2008/09||% change since 2016/17|
|Comparable SCJS Crime||731,000||448,000||386,000||-47%||No change|
|Comparable Recorded Crime||215,901||131,566||130,418||-40%||-1%|
|SCJS Acquisitive Crime||64,000||51,000||51,000||No change||No change|
|Recorded Acquisitive Crime||27,527||18,295||17,867||-35%||-2%|
|SCJS Violent Crime||317,000||231,000||172,000||-46%||No change|
|Recorded Violent Crime||82,855||63,246||63,835||-23%||1%|
|SCJS Vandalism||350,000||166,000||163,000||-54%||No change|
Sources: SCJS; Police recorded crime; SCJS Base: 2008/09 (16,000); 2016/17 (5,570); 2017/18 (5,480)
Note: changes specified where statistically significant.
The acquisitive comparable crime group includes bicycle theft, housebreaking and theft of a motor vehicle. In 2017/18, the SCJS estimated that there were 51,000 acquisitive crimes (+/- 13,000, meaning that the true number of acquisitive crimes in the underlying population is estimated to be between 38,000 and 65,000). The police recorded 17,867 acquisitive crimes in 2017/18.
Recorded acquisitive crime fell by 35% between 2008/09 and 2017/18, and by 2% between 2016/17 and 2017/18. No statistically significant changes were identified in SCJS acquisitive crime across either of these time periods, however this is likely in part due to the smaller sample sizes involved which mean that it can be more challenging to identify significant differences over time.
Violent comparable crime includes serious assault, minor assault and robbery. In 2017/18, the SCJS estimated that there were 172,000 violent crimes (+/- 47,000, meaning that the true number of violent crimes in the underlying population is estimated to be between 125,000 and 219,000), while the police recorded 63,835 violent crimes.
Table 5.1 shows that the two sources of comparable violent crime data both show large decreases over the longer term, but broadly stable figures since 2016/17. Between 2008/09 and 2017/18, both SCJS estimates and recorded crime violent crime figures have shown a decrease (by 46% and 23% respectively). Since 2016/17, recorded violent crime has increased by 1%, while the SCJS has found no change in violent crime.
The vandalism comparable crime group includes motor vehicle vandalism and property vandalism. In 2017/18, the SCJS estimated that there were 163,000 instances of vandalism (+/- 29,000, meaning that the true number of vandalism crimes in the underlying population is estimated to be between 134,000 and 192,000). The police recorded 48,716 vandalism crimes in 2017/18.
There is strong consistency in the trends in comparable vandalism crime across both SCJS and police recorded crime between 2008/09 and 2017/18 – with both showing decreases of 54% over this period. Since 2016/17, there has been no change in the SCJS estimate of vandalism, while crimes of vandalism recorded by the police have fallen by 3%.
The number of SCJS crimes estimated to have been reported to the police is similar to, but slightly greater than, the number of police recorded crimes.
An alternative approach to investigating the relationship between the two sources is to examine the amount and ratio of police recorded crime to the volume of SCJS crime estimated to have been reported to the police.
SCJS respondents are asked whether the police ‘came to know about’ the crime, either from them or somebody else. This allows comparisons to be made between comparable crime estimated to have been reported to the police in the SCJS (i.e. a subset of comparable crime), and police recorded crime figures.
The analytical paper, published in 2014, outlined two methods for calculating this: the first, comparing the biennial SCJS to annual recorded crime figures and the second comparing the biennial SCJS against two financial years of averaged police recorded crime data. This section updates the information using the first method, to compare now annual SCJS estimates to annual recorded crime figures. Although it is not possible to determine on an individual basis whether a crime that the police ‘came to know about’ was captured in police recorded crime data, this type of analysis can give an indication of the level of crime that goes unreported, and the broad relationship between police recorded crime figures and SCJS estimates.
Figures from the 2017/18 SCJS indicate that of the 386,000 crimes in the overall comparable subset, around 155,000 incidents (40%) were estimated to have been reported to police. In 2017/18, the police recorded 130,418 crimes in the comparable category. It is therefore estimated that around 84% of comparable crime estimated to be reported to the police was recorded by the police in 2017/18. This figure has varied over the last decade, ranging from 62% (in 2012/13) to 78% (in 2009/10) – with the 2017/18 figure therefore being the highest value to date.
Figure 5.2: Ratio between police recorded crime and SCJS crime estimated to have been reported to the police 2008/09 to 2017/18
Sources: SCJS; Police recorded crime.
In addition, as a proportion of all SCJS comparable crime, the amount of comparable crime estimated to have been reported to the police, and not recorded in police statistics, was 6% (or around 25,000 incidents) in 2017/18. This figure has varied a little in previous years, between 9% (in 2009/10) and 17% (in 2012/13) – although based on a different total figure for each year.
Figure 5.3: Recorded crime, SCJS crime and SCJS crime reported to the police, in the set of comparable crimes, 2008/09 to 2017/18
Sources: SCJS; Police recorded crime.
This type of analysis can be extended across the comparable crime sub-groups, where similar results are found. For example, around 67,000 violent crimes are estimated to have been reported to the police in 2017/18 (or 39% of the number of violent crimes estimated by the SCJS), while the police recorded 63,835 violent crimes. It is therefore estimated that almost all (96%) of comparable violent crime estimated to be reported to the police was recorded by the police in 2017/18. This figure has previously ranged from 58% (in 2012/13) to 79% (in 2009/10).