Appendix – Further details of the method

This appendix gives more details of the methods employed in this study.

Categories of crime

For the purposes of this study, crime has been broken down into three main categories:

• offences against the person: violent offences, sexual offences and robbery;
• offences against private property: burglary, theft, property damage and fraud;
• offences with no direct or intended victim: drug offences, serious traffic offences and all other offences.

Some of these categories have a number of sub-categories, which are described more fully below. Within each there is a range/continuum of seriousness, which is necessarily masked through aggregation. More detailed statistics are available from sector publications.

Apportioning justice sector spending across the categories of crime

Apportioning total spending across each of the relevant crime categories has been calculated as follows for each of the core justice sector agencies:

• Police – the actual cost of Police time per category of offence multiplied by the number of recorded offences per category;
• Courts – total spending on criminal cases weighted for each crime category by the ratio of convicted cases for that category to total convicted cases;
• Justice and Crown entities – same as for Courts;
• Corrections – total spending weighted for each crime category by the ratio of inmates sentenced for crimes of that category to total sentenced inmates;
• CLO, CYF – on an apportionment basis provided by the agencies.

Multipliers

The most recent crime survey data for New Zealand relates to 2001. The multipliers from that survey have not been used in this study, as they are generally not readily convertible to the crime sub-categories used here and/or are not available for those sub-categories.

Instead, comparable multipliers from either the UK (2003/04) or Australia (2000/01) have been used, where appropriate. This assumes that the percentage of crimes officially reported in the UK and Australia are similar to the New Zealand experience (which may or may not be the case). Judgement has been used in choosing the appropriate multipliers, so the resultant costs of crime estimates are at best indicative. Where there are comparable New Zealand multipliers, this is noted below.

Note that most of the multipliers used here have been based on surveys of individuals and households, and exclude businesses and institutions. In the absence of any further information on incidents of property crime against businesses and institutions, it is assumed that the applicable individual/household-based multiplier can be applied to businesses as well (e.g. non-residential burglaries, arsons, etc. are as likely to be reported as residential ones).

Violent offences

This category comprises homicide, grievous assault, intimidation/threats, kidnapping and abduction and other assaults. There were 43,231 recorded violent incidents in New Zealand in 2003/04, made up of 100 homicides, 3,351 grievous assaults, 10,901 incidents of intimidation/threats, 214 incidents of kidnapping and abduction and 28,665 other (serious and minor) assaults.

For both homicide and kidnapping and abduction it is assumed that all actual incidents are reported to the Police (i.e. they are recorded). For grievous assaults a multiplier of 1.8 is assumed (this is the 2003/04 UK multiplier for ‘serious wounding’). For other assaults a multiplier of 7.7 is assumed (this is the 2003/04 UK multiplier for ‘common assault’). This last multiplier has also been assumed for intimidation/threats.

Applying these multipliers brings the estimated total number of violent crimes in New Zealand in 2003/04 to 311,000. Derived average private sector, public sector and total costs for each category of violent offences are shown in Appendix Table 1.

Sexual offences

This category includes sexual violation and other sexual offences (i.e. sexual attacks and affronts, acts of immoral behaviour, etc.). There were 3,179 recorded sexual offences in New Zealand in 2003/04, made up of 832 sexual violations and 2,347 other sexual offences.

The relevant multipliers for the UK in 2003/04 (‘sexual offences’) and Australia in 2000/01 (‘sexual assault’) are similar, at 5.2 and 5.6 respectively. We have used the UK multiplier (5.2) as it is the more recent.

However, it is important to estimate sexual violation (rape, etc.) separately from other sexual offences, as the individual costs relating to the former tend to be much higher. Thus sub-multipliers of 1.5 and 6.5 (approximately) have been derived for sexual violations and other sexual offences respectively (together these give a weighted average of 5.2) on the assumption that the former are more serious and so more likely to be reported/recorded than the latter. This assumes that two thirds of all sexual violations are recorded.

Applying these multipliers brings the estimated total number of sexual offences in New Zealand in 2003/04 to 16,500 (comprising about 1,200 sexual violations and 15,300 other sexual offences). Derived average private sector, public sector and total costs for each category of sexual offences are shown in Appendix Table 2.

Robbery

Robbery is defined as the act or process of taking unlawfully by force or threat of force. Hence it is a crime against the person, even though property typically changes hands. There were 1,835 recorded incidents of robbery in New Zealand in 2003/04.

A multiplier of 3.7 is assumed (this is the 2003/04 UK multiplier for ‘robbery’), bringing the estimated total number of robberies in New Zealand in 2003/04 to 6,800.

Burglary

Burglary is defined as illegal entry into a building with intent to commit theft or do damage. There were 60,630 recorded incidents of burglary in New Zealand in 2003/04.

A multiplier of 2.2 is assumed (this is the 2003/04 UK multiplier for ‘burglary in a dwelling’, which is not dissimilar from the 2.5 multiplier from the NZ National Survey of Crime Victims 2001), bringing the estimated total number of robberies in New Zealand in 2003/04 to 133,400. As noted earlier, it is assumed that non-residential burglaries from businesses, etc. are equally likely to be reported to and recorded by the Police as residential ones. The relatively low magnitude of this multiplier is plausible, given that burglaries are required to be reported to the Police for insurance purposes.