While there appears little doubt that an age-crime pattern exists and that it is very robust, the actual nature of the association (that is, whether it is variant or invariant) remains unclear and widely contested. There are many layers to the original arguments concerning the variance or invariance of the association, which continue to be central to age-related analyses of crime. The subsequent contributions to the subject, be they direct responses to Greenberg or Hirschi and Gottfredson, or broader applications of their arguments, are yet to clarify whether the age-crime pattern is variant or invariant. In fact, the nature of the age-crime pattern may be even more complex than either Greenberg or Hirschi and Gottfredson anticipated, as it appears there may be some validity to both theses. This is also suggested by Blumstein (2005: 246), who acknowledges ‘the desirability of pursuing both directions until we find some optimum mixture’. Indeed, the interpretation of official crime statistics, the type and level of data consulted, and areas of interest all appear to influence how the association between age and crime is perceived.
It is not intended in this thesis to explore all of the complexities of the variant and invariant theses developed by Greenberg and Hirschi and Gottfredson (this thesis being more concerned with the age structure-crime pattern). However, the arguments that their theories raise, and the subsequent studies of the variance/invariance debate, demonstrate the need for this thesis’s investigation of the age structure-crime pattern to be constructed – and, subsequently, interpreted – in a manner that allows for either (or both) a variant or invariant association between age and crime to exist. Accordingly, it is possible that neither position will be fully supported or negated; rather, investigation of the age structure-crime pattern is more likely to determine that one, if not both, of the variant/invariant constructs is plausible.
This will be explained in greater detail as this thesis progresses, specifically when the conceptual and analytical frameworks are developed in Chapters 3 and 6 (following, respectively, discussions of the Easterlin hypothesis and how data availability shapes the proposed course of analysis). However, this thesis can address the nature of the age-crime pattern in two ways. The first of these relates to the potential for
demographic phenomena to impress upon age-crime trends which, although not explicitly discussed in the age-crime literature raised here, is implied. Greenberg (1983, 1985) refers to cohort effects as a potential source of variation in the age- crime pattern. Thus, it would seem plausible that the impact of cohort density on age- specific apprehension rates (which will be discussed in greater detail in relation to the Easterlin hypothesis in Chapter 3) could be regarded as a potential source of variance for the age-crime pattern. Indeed, O’Brien and Stockard (2009) determined that the association between cohort replacement and the age-crime curve for homicide indicated that the age-crime pattern is not ‘rigidly invariant’; Sampson and Laub (1993; also Laub and Sampson 2003) similarly show that job stability (which is associated with cohort density, as will be seen in Chapter 3) is a source of variance for age-crime trends.
The second means of addressing the variance/invariance debate is more general. It relates to whether differences in the impact of structural ageing are indicated in this thesis’s analysis of the age structure-crime pattern. A variant association between age and crime would be indicated by any of the following:
1. Age-crime trends change over time. This type of change would suggest that such trends are influenced by factors such as demographic change (i.e. structural ageing), social and/or life events (such as relative disadvantage (unemployment, for example)), and/or historical processes (such as changes in the surveillance methods of the criminal justice system, or the willingness of victims to report crime).
2. The impact of structural ageing differs by offence. Such variation would be indicative of some offences having an older age distribution of offenders than others, which may be related to differences in the peak age of offending and/or the process of desistance (the ‘ageing out of crime’) across offence types.
3. The impact of structural ageing differs by gender. For example, males may be more likely to deviate from the age-crime pattern than females for a particular offence. Such a finding may be indicative of differences in the impact of either demographic change, social and/or life events, and/or historical
processes on male and female apprehension trends, and/or differences in the age distribution of offenders for the sexes.
On the other hand, if there are only minor, or no, differences in age-crime trends over time, or the impact of structural ageing by offence and gender (suggesting, for example, that the impact of demographic, social and/or life events, and/or criminal justice factors does not change over time, and/or the age distribution of offenders is relatively homogenous by offence and gender), then the association between age and crime could be regarded as being relatively homogenous.
The following chapter focuses on the age structure-crime pattern, outlining the expectations regarding the impact of cohort density and age composition for the Australian population in light of the Easterlin hypothesis. This includes discussion of how the nature and strength of the age-crime pattern may shape the association between structural ageing and crime.