The aim of national crime statistics is to provide comparable data across the States and Territories. These statistics cover selected crimes recorded by State and Territory police in Australia and provide a measure of the level and nature of crime in Australia.
Two sources of national statistics provide a picture of crime in Australia: crimes recorded by police, and crime victimisation surveys. Crimes recorded by police relate to offences that have become known to and have been recorded by police. These offences may have been reported by a victim, witness or other person, or they may have been detected by police. These statistics do not provide a total picture of crime, as not all crimes come to the attention of police. In addition, care should be taken in interpreting police statistics, as fluctuations in recorded crime may be a reflection of changes in community attitudes to reporting crime, changes in police procedures or changes in crime recording systems, rather than a change in the incidence of criminal behaviour. Significant events occurring in particular years may also contribute to fluctuations in recorded crime.
To gain a more comprehensive picture of the nature and extent of crime, police statistics are complemented by information from other sources such as crime victimisation surveys. These surveys are conducted on a household basis and collect information on crimes of which people know they have been victims (and can recall the incident/s), whether or not they reported the crimes to the police. Crime victimisation surveys allow crime information to be related to personal and household characteristics, and facilitate the study of patterns of victimisation over time and across crime categories.
Not all types of crime are suitable for measurement by household surveys. No reliable information can be obtained about crimes where there is no specific victim (eg trafficking in narcotics). Crimes of which the victim may not be aware cannot be measured effectively; some instances of fraud and many types of attempted crimes fall into this category. It may also be difficult to obtain information about some crimes, such as sexual offences and assault by other household members, so that some of these crimes are not fully reflected in the data collected. Finally, no reliable data can be collected by household surveys on crimes against commercial establishments.
In essence, crime victimisation surveys are more suitable for measuring crimes against individuals or households with specific victims who are aware of and recall the incident and how it happened, and who are willing to relate what they know.