Age and the prevalence of delinquency

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Figure 3 shows the proportions of each birth cohort who were identified by police as offenders, at each year of age. The trajectories for the two cohorts are so similar that they can be treated as coming from the same population.¹ Participation in police-reported crime is very low at the younger ages: only 0.033%, or one in every 3,000 5 year olds, were recorded by police as being implicated in a crime.² Participation increases slowly to the age of 11, when 0.7% of the combined cohorts, or one in every 140 members, were apprehended by police. After the age of 11, the prevalence of recorded criminal behaviour increases much more rapidly. At the peak age of 16, 5.8%, or one in every 17 members of the 1987 cohort were apprehended by police. There is little difference in the level of participation in recorded delinquency among 15, 16, and 17 year olds.

Figure 4 shows the rate of change in prevalence of recorded delinquency, relative to the level in the preceding year.³ The very large increase of 139% from 11 to 12 years old may reflect under-recording of crime committed by children younger than 12, rather than a sudden increase among 12 year olds, since it is unlikely that the twelfth birthday would induce a large increase in actual criminal activity. Rather, under the legislation in force during this period (the Young Offenders Act and Youth Criminal Justice Act), the minimum age of criminal responsibility was 12 years old at the time of the alleged offence. Police were unable to lay a criminal charge against identified offenders who were less than 12 years old. This may have affected both their identification of children as offenders, and their recording of such identifications.⁴ Apart from the large increase at 12, relative increases in participation are greatest at the youngest ages – 6 and 7 years. After the age of 12, relative increases in participation decrease rapidly, becoming negative at 17.

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Notes

1. Two-tailed t-values for the differences in prevalence at ages 8, 9, ..., 14, are 1.95, -1.36, 1.51, -1.85, 1.74, 1.65, 6.08. These statistics should be interpreted with caution, since these are not normally distributed random samples. Satterthwaite's (1946) approximation for the degrees of freedom was used, since the variances of each pair of vectors of observations were unequal (SAS Institute, 2004). Only the t-value for 14 year olds is significant at p<.05 (p₁₄<.0001). This is probably due to a slight under-counting of offences in the data for 2005; see the preceding note.
2. To some extent, the low participation in recorded crime by children may reflect the process by which crime comes to be recorded by police. Most crime which comes to the attention of the police is reported by members of the public. If members of the public are less likely to report the minor crimes which are committed by younger children, then they will be under-represented in police statistics. Furthermore, police may be less likely to record the minor crimes which are committed by younger children, even when they are reported to police by the public (see the discussion in note 4 below of the jump in recorded crime at 12 years of age, shown in Figure 4).
3. Defined as: (x_t - x_t-1)/x_t-1, where x_t is the proportion of the cohort recorded as offenders at age t.
4. It is possible that less police resources would be devoted to investigating minor incidents involving  child perpetrators, and establishing their identities, since no charges could result. Also, even if the perpetrators' identities were known, police officers have some discretion in deciding whether or not to record a minor incident and its participants, particularly if the incident has not been referred to them by police dispatchers, and is therefore not already recorded on the police information system (Carrington and Schulenberg, 2003). In incidents involving child perpetrators, there is less incentive to go to the trouble of recording the incident and their names in the police information system, because they would not be chargeable. For both of these reasons, UCR2 counts of offenders under 12 years old may be underestimates, giving rise to a jump in recorded participation at the age of 12.