Mainstreaming Methodology for Estimating Costs of Crime
There are many components in a costs of crime model. We recommend the following strategy for approaching the task.
1. Specify Objectives
You need first to specify your principal objectives for measuring the costs of crime. There are several possible motivations. The choice of methodology needs to reflect your purpose. For example, you might be wanting to:
Be clear about your purpose and resist the temptation to try too much, particularly the first time. The design of this site is oriented primarily to meeting the first of these objectives.
2. Decide on offence coverage
You need to decide how wide you wish your coverage to be in terms of the types of crime included. Many well-known studies of the costs of crime focus on crime against the individual and the household. This covers a wide range of offences but it also excludes many potentially important sources of cost such as crime against business and crime against the government in the form of tax evasion, corruption and so on. The choice of coverage will reflect the objectives of your study. But it is important to note that the wider you cast the net the bigger the task of cost estimation.
There are two key decisions to make. First, as already discussed, is the choice of which broad offence categories to include: for example, whether to include crime against business and government. Secondly there is the choice as to how much aggregation to do within broad offence categories. For example will you treat violence against the person as a single category or do you split it down into many small offence types (such as 'serious wounding' or 'violence resulting in an interrpution of normal activities for seven days or more' or whatever).
Steps along the way need to include:
The full set of categories is likely to be very lengthy and to include some components that are of less pressing importance. It is essential to be realistic about how many categories you can cover and useful to prioritise the remaining areas you propose to cover.
3. Conduct Data Audit
You need next to establish a very clear picture of the data you have available. See a separate document outliniing a Strategy for compiling a data audit.
4. Estimate the Volume of Offences
The next step is to make an estimate of the volume of offences committed. This process involves a significant amount of detail so it, too, is outlined in a separate document: see Estimating the Volume of Offences.
5. Estimate the Gross Costs per Offence
The single largest step is to build a model for cost estimation. In essence this involves taking each offence type in turn and making an estimate for every cost line, as set out in our taxonomy. One way of visualising this is to think of a spreadsheet model in which there is a worksheet for each offence type. Each of these worksheets has an area used for parameter input values plus a row for each cost component (e.g. property stolen or cost of imprisoning those found guilty of the offence). Some of these lines may refer to other areas of the worksheet where detailed calculations are performed (e.g. a Present Value calculation of imprisonment costs based on the number of persons imprisoned for the offence and the average prison term length). The gross costs to victims (and quite often too the costs of steps taken by the population to avoid harm from crime) are estimated usually from victim survey evidence. Gross costs to the Criminal Justice System are estimated from reports and government statistical sources.
6. Produce Estimates of Costs per Offence
The final step is to tabulate your calculations in a format that is helpful for end-users. The standard layout is to distinguish the three principal categories of costs plus the total broken down by offence types. The size of the table will typically be four columns for cost categories and one row for each of the offence types for which estimates have been made. Since this latter depends on the local legal system and on the quality of data available there is no magic formula for the number of rows. The table is populated with summary values by cost category linked from the individual worksheets described at step 5 above.
