Background

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This is the first large-scale study in Canada which uses police-reported data to examine the development of criminal behaviour during childhood and adolescence. A companion study (Carrington et al., 2005) examines criminal behaviour during adolescence and early adulthood, using data from youth and adult court records. The study population whose recorded delinquency forms the subject matter of the present report consists of two groups of Canadian youth,¹ born in 1987 and 1990. Each person's police-reported delinquency is tracked for 10 years, beginning on his or her birthday in 1995 and ending on the day before the birthday in 2005. Those who were born in 1987 are tracked from their 8^th birthdays until the day before their 18^th birthdays, and those born in 1990 are followed from their 5^th birthdays to the day before their 15^th birthdays. Only those crimes committed and recorded within the jurisdictional boundaries of police services reporting to the Incident-Based Uniform Crime Reporting Survey (UCR2) during 1995-2005 are included in the study. On average, during the period from 1995 to 2005, 52% of the population of Canada lived in the parts of Canada included in this study.

In the past, most studies of delinquency² took as their unit of analysis either the delinquent individual or the delinquent act. Over the past two or three decades, a new approach to the study of delinquency and adult crime, called life-course criminology, has introduced a new unit of analysis: the delinquent or criminal career. The criminal career is defined as the sequence of criminal acts perpetrated by the same individual over his or her life. In practice, almost no research on criminal careers has had access to data on individuals' entire life-spans,³ and almost all studies have been restricted to the period from childhood or early adolescence to the end of adolescence or some point during early- or mid-adulthood. Many criminal career studies, including the present one, restrict their study population to the members of one or a few birth cohorts – that is, persons who are all born in the same year, or in a few selected years - in order to study the development of criminal behaviour of a group or groups of persons who are all passing through the same part(s) of the life-course during the same historical period.

The study addresses the following questions concerning the development of criminality in Canadian youth:

• How much recorded crime are Canadian youth responsible for? What are the predominant types of recorded youth crime? How does the youth crime rate vary by the sex and age of offenders?
• What proportion of Canadian youth are involved in recorded crime? How does the level of participation vary over childhood and adolescence, by the sex of the offender, and by the type of crime?
• How much recorded crime does an average young offender commit during his or her childhood and adolescence? – and how much variation is there from the average? Do some young offenders commit very little crime, and others commit a great deal? Are the variations related to the age and/or sex of the young person? For example, is the average rate of offending higher or lower in childhood than in adolescence? Are there variations with age and/or sex in the rate of commission of different types of crimes?
• At what age do young people commit their first recorded crime? Does this tend to be during childhood or adolescence? Does this "age of onset" vary by sex? Does the first recorded offence tend to be a certain type of crime? Is there a relationship between the age of onset and the total amount of crime committed during the delinquent career?
• How much time elapses between the first and last recorded offences in the average delinquent career? Do these careers tend to continue for years or are they typically of short duration? Does the duration of the career vary with the sex of the offender? Does it vary with the age of onset?
• Do young offenders tend to specialize in one type of crime, or are they typically versatile in their recorded criminal behaviour?
• Do children and adolescents tend to "graduate" from less serious to more serious types of crime?

It should be emphasized that this study relies on police-reported data on alleged offenders and crime. Therefore, only those crimes which come to the attention of the police, and in connection with which a child or adolescent accused is identified, are included in the study. These persons are referred to in the report as "accused" or "alleged offenders", because the data indicate only whether a person was identified by police as an offender, i.e. was "accused", not whether he or she actually committed an offence. According to the 1999 General Social Survey on Victimization, which was conducted at approximately the mid-point of the period covered by the present study, 59% of criminal victimizations in Canada were not reported to the police (Besserer & Trainor, 2000). In addition, an unknown proportion of "victimless" crimes, such as drug crimes and public order crimes were not reported to police. According to the 1999 Uniform Crime Reporting Survey, 60% of criminal incidents recorded by the police were not "cleared": that is, no offender was identified (Canadian Centre for Justice Statistics, 2000).

The data were extracted from the information systems of police services in Canada which participate in the Incident-Based Uniform Crime Reporting Survey. During the period covered by the study, these respondents provided policing services to approximately half of the population of Canada, mainly in the provinces of Québec and Ontario. Therefore, the data are not necessarily representative of all of Canada. However, the youth crime rate and distribution of types of recorded youth crime in the parts of Canada included in this study do not differ substantially from the youth crime rate and types of youth crime for Canada as a whole. This issue is discussed in "Delinquency in the Study Population and the National Population".

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Notes

1. Strictly speaking, the subjects of the study are persons born in 1987 or 1990 who allegedly committed criminal offences in the parts of Canada included in the study. These persons were not necessarily born in Canada, or even resident in Canada.
2. In this report, which deals exclusively with the police-reported criminal behaviour of persons younger than 18 years old, the terms "delinquency" and "crime" are used interchangeably.
3. The exception is a study by Laub & Sampson (2003), which followed a sample of delinquent boys to their 70^th birthday, or their death, if it occurred earlier.