Reconviction rates in Scotland: 2013-2014 offender cohort

3. Comparing reconviction rates across administrative areas

( Table 11)

The reconviction rate for an administrative area is based on information for offenders convicted in courts that fall within that administrative area's boundary. Typically an offender would go to a court located in the same administrative area in which they live, though occasionally an offender may be seen by a court located in a different administrative area. Similarly an offender may not always be supervised in the area in which they are convicted and subsequent reconvictions may have occurred in different areas. In addition, the areas that courts serve don't exactly match administrative areas for Local Authorities or Community Justice Authorities ( CJAs) (see Annex A10 and the footnote of Table 11).

Reconviction rates vary across administrative areas (based on court location). Table 11 and show that the highest reconviction rate in the 2013-14 cohort was for offenders whose index conviction was given at courts in both the Clackmannanshire and Dundee City areas (32.8 per cent each), with the former having the highest average number of convictions per offender (0.66). The lowest reconviction rate (13.8 per cent), and lowest average number of reconvictions per offender (0.18), were both for offenders whose index conviction was given at a court in the Orkney Islands. These are unadjusted figures which do not take account of underlying differences in population size and the characteristics of offenders in each area. It should also be noted that several Local Authorities have small numbers of offenders, within which small between year fluctuations in the numbers of offenders reconvicted may lead to larger changes in the reconviction rate and average number of reconvictions per offender than for Local Authorities with larger numbers of offenders.

Table 11 also includes measures of the reconviction rate and average number of reconvictions per offender at the Community Justice Authority ( CJA) level for the 2013-14 cohort. It shows that the highest average number of reconvictions per offender (0.58) and highest reconviction rate (30.1 per cent) were both in the Glasgow CJA. The lowest average number of reconvictions per offender (0.44) and the lowest reconviction rate (25.1 per cent) are for the Northern CJA.

3.1 Accounting for the variability between local authorities

Reconviction rates are a Scottish Government National Indicator on Scotland Performs. As such, they are commonly used to rank performance across different jurisdictions, such as Community Justice Authorities and Local Authorities. However, there is an inherent problem in using this approach since it implicitly assumes that a difference in reconviction rate reflects a 'real' difference between organisations. In reality, all systems within which these organisations operate, no matter how stable, will produce variable outcomes in the normal run of events. In particular, outcomes in jurisdictions with smaller sized populations tend to vary more than those in jurisdictions with larger populations. The question we need to answer is therefore: Is the observed variation more or less than we would normally expect?

In this respect, it is better to use a method of comparison that takes account of inherent variability between jurisdictions ^[5] . The funnel plot is a simple statistical method that takes into account the variability of different sized populations and so highlights whether there are differences that may be attributed to some other special cause ^[6] .

Table 11 shows the average number of reconvictions per offender and reconviction rates for each Local Authority group and Chart 8 shows the reconviction rates against the number of offenders. The plot takes into account the increased variability of the Local Authorities with smaller populations, where a small increase in the number of reconvictions may lead to a large percentage change in the reconviction rate. Rates for Local Authorities which lie inside the funnel are not significantly different from the national rate, and we can then usefully focus on possible explanations for rates which deviate significantly from the national figure. In this case, the cut-off level for statistical significance is 95 per cent (or two standard deviations from the mean): if there were no difference between Local Authorities apart from that which could reasonably be attributed to random variation, we would expect that 5 per cent of the authorities (i.e. only 1 of them) would lie outside the funnel.

Chart 8 shows that Dundee City, Glasgow City, and Fife lie above the funnel, and so have higher reconviction rates than expected. Aberdeen, Highland, Moray, Perth and Kinross, Na h-Eileanan Siar, the Shetland Islands and the Orkney Islands lie below the funnel and so have lower rates than expected. Whilst this is useful for highlighting that there are practical differences in reconviction rates between each Local Authority, even after taking into account differences in population sizes, it does not allow us to identify if this disparity is due to variation in the characteristics of offenders in each area or a variation in practices between different Local Authorities. Different offender characteristics between Local Authorities could include: age, gender, crime, disposal, ethnicity, deprivation, etc.

Chart 8: Reconviction rates by Local Authority group: 2013-14 cohort ^[7]

Chart 9 is standardised to take into account differences between Local Authorities attributable to the characteristics of offenders, such as the number of previous offences, sentence, gender, and age. It provides the standardised reconviction rates ^[8] against the observed number of offenders minus expected number of offenders. Since all Local Authorities are within the funnel it suggests that the apparent differences in reconviction rates in Chart 8 are primarily attributable to either the variation in the characteristics of the offenders, the type of crime they committed, or the sentence they received, rather than differences in 'performance' between the Local Authorities. This overall conclusion for all local authorities on the 2013-14 cohort is consistent with the findings of the 2012-13 cohort provided in the Reconviction Rates in Scotland: 2012-13 Offender Cohort publication. Previous publications that have presented findings at the CJA level, also showed that CJAs were within the funnels with either one year (the 2013 and 2012 reconvictions publications) or two year reconviction rates (the 2011 reconvictions publication).

Chart 9: Standardised reconviction rates by Local Authority group: 2013-14 cohort ^[8]