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Crime and demographic change

Media Release

29 February 2012

The Australian Institute of Criminology (AIC) today published two research reports on the link between crime and population change.

The author, AIC Researcher Dr Lisa Rosevear, investigated how the ageing of the South Australian population affected general crime levels. In the second report, Dr Rosevear examined crime rates in Western Australia and how large birth cohorts affect crime patterns as they age.

Studies such as these inform long-term planning for Commonwealth and State criminal justice agencies. They assist in gauging crime prevalence as populations age, and the resulting impacts on government budgets through policing, corrections, rehabilitation and diversion.

The SA study considered that by 2026 the proportion of individuals over 65 years in Australia will have grown by 90 percent compared with 11 percent for all other age groups combined and concludes that as the population ages crime rates will reduce.

“The data showed that overall, arrest rates go up when a population is younger and go down when it is older. These results hold for both males and females. Arrest rates can be broken down by crime category as well.

“The effect of structural ageing generally had the greatest impact on offences against property, as well as robbery and extortion for males. However, little effect on sexual offences (committed mainly by males) was evident,” Dr Rosevear said.

All Australian states and territories have experienced structural ageing, although not uniformly - the population of the Northern Territory is much younger and the populations of Tasmania and South Australia somewhat older than the national population.

The WA study uses the population to illustrate the extent to which Australia’s largest cohort after the ‘baby boomers’ (the so-called ‘baby bust’ cohort) has engaged in higher levels of criminal activity compared with smaller birth cohorts.

One of the largest birth cohorts was born between 1969 and 1972. WA arrest data between 1994 and 2002 indicates that this cohort experienced arrest ratios that did not decline as the cohort aged, where a decline in offending would normally be expected.

This large cohort encountered a poor labour market in the late teens, which would have increased the likelihood of cohort members competing with each other and experiencing disadvantage and associated stress levels.

The study suggested that the size of the actual cohort had a greater impact on males, while other relative elements, such as unemployment and education, had more of an adverse effect on females.

“That birth cohorts impact criminal behaviour is useful for understanding how and why certain groups of people come into contact with the criminal justice at later ages and this information may be used in criminal justice resource allocation decisions,” Dr Rosevear said.

“Australia has over time experienced waves of differently sized birth cohorts, yet the impact of these waves on long-term crime trends is frequently overlooked,” Dr Rosevear said.

AIC media contact: Colin Campbell 02 6260 9244 / 0418 159 525