6 Comparing reconviction rates across administrative areas
6.1 Reconviction rates vary across administrative areas (based on court location). However, it is important to note that an offender may not always be supervised in the area in which they are convicted and subsequent reconvictions may have occurred in different areas. The characteristics of offenders are also likely to vary across these areas, therefore such comparisons between areas should be treated with caution, and it is suggested that a method which takes these factors into account should be employed (see below).
6.2 The areas that courts serve don't exactly match administrative areas for Local Authorities or Community Justice Authorities (CJAs). For example, Edinburgh Sheriff Court serves the Local Authority areas of the City of Edinburgh and Midlothian; and Glasgow Sheriff Court, which covers the Glasgow CJA, also covers parts of East Dunbartonshire which are in the North Strathclyde CJA. Therefore in Table 10, Chart 7, and Chart 8 in this bulletin, CJAs and Local Authorities are based on approximate areas. Therefore, some Local Authorities are grouped together so that there are 25 groups of Local Authorities presented, rather than all 32 being displayed separately. See the footnote of Table 10 for details of the approximations for each administrative area.
6.3 Table 10 shows that the highest reconviction rate in the 2011-12 cohort was for offenders whose index conviction was given at courts in the Dundee City area (35.8 per cent), and the highest average number of convictions per offender was in the Clackmannanshire area (0.70). The lowest reconviction rate (21.3 per cent), and lowest average number of reconvictions (0.32), was for offenders whose index conviction was given at a court in East Lothian. These are unadjusted figures which do not take account of underlying differences in population size and the characteristics of offenders in each area.
6.4 Table 10 also includes measures of the reconviction rate and average number of reconvictions per offender at the Community Justice Authority (CJA) level for the 2011-12 cohort. It shows that the highest average number of reconvictions per offender is in the Glasgow CJA (0.62) and highest reconviction rate is in the Tayside CJA (32.6 per cent). The lowest average number of reconvictions per offender (0.41) and the lowest reconviction rate (24.3 per cent) is for the Lothian and Borders CJA.
6.5 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 rates 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?
6.6 In this respect, it is better to use a method of comparison that takes account of inherent variability between jurisdictions. 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.
6.7 Table 10 shows the average number of reconvictions per offender and reconviction rates for each Local Authority group and Chart 7 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.
6.8 Chart 7 shows that five Local Authorities: Clackmannanshire, Dundee City, Falkirk, Glasgow City, and Stirling) lie above the funnel and so have higher reconviction rates than expected. Argyll & Bute, East Lothian, Edinburgh and Midlothian, Highland, Scottish Borders, and West Lothian 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.
6.9 Chart 8 is standardised to take into account of 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 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 7 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 2011-12 cohort is consistent with the findings provided in the 2011 reconvictions publication (which provided funnel plots on the two year reconviction rates for the 2007-08 cohort); and the 2012 reconvictions publication (which provided funnel plots on the one year reconviction rates for the 2009-10 cohort). Although these previous finding presented reconvictions at the CJA level, all CJAs were within the funnels.
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