La concentración de delitos parece que sigue el principio de Pareto: el 20% de los individuos de una población son responsables del 80% de los delitos (y el 10% comete el 66%)
We began our analysis by comparing the cumulative distributions of offending prevalence and frequency across all our studies. We calculated the prevalence and frequency curves using 154 data points from 15 studies and 288 data points from 27 studies, respectively. In Fig. 2, the solid line represents the prevalence curve and the dashed line represents the frequency curve. The prevalence curve represents the distribution of offending across a “population” containing both offenders and non-offenders. In contrast, the frequency curve reflects the crime concentration only among individuals who have committed at least one offense (i.e., offenders). The prevalence distribution shows more crime concentration than the frequency distribution. This is expected given that offending is a rare occurrence (i.e., most people in the population do not commit crime). For example, the 10% of the most criminally-active people account for around 66% of crime, whereas the most active 10% of offenders account for around 41% of crime (see Fig. 2).
Fig. 2 | Overall prevalence and frequency of offending
Youths and adults
Research has shown that involvement in offending differs between youths10 and adults. The prevalence of offending tends to reach its peak in late adolescence and then declines rapidly by early adulthood.11 This pattern is commonly referred to as the “age-crime curve” (Farrington 1986; Hirschi and Gottfredson 1983; Piquero et al. 2003). Hirschi and Gottfredson (1983) contend that the age-crime curve is invariant, meaning that the pattern of involvement is the same for all types of offenders. If the prevalence of offending follows a stable pattern that predicts a sharp decline in early adulthood, then there would be no need to examine changes in offending over the life course through criminal career research (Rocque et al. 2015a). Although youths are more likely than adults to be involved in crime, it is unclear whether the prevalence of offending differs within each group.
It is also unclear whether youths and adults differ in the frequency of their offending. Hirschi and Gottfredson (1983) claim that the frequency of offending follows the same pattern as prevalence. In other words, the sharp decline in the age-crime curve that occurs in early adulthood reflects both a decrease in the prevalence of offending and a decrease in the frequency of offending (Piquero et al. 2003). However, the research on offending generally does not support this view (for a review, see Piquero et al. 2003). In contrast, Blumstein et al. (1988) argue that while the decline could be the result of a large proportion of offenders desisting from crime as young adults, this does not mean that those who continue to offend necessarily do so less frequently.
To examine these potential differences in offending prevalence and frequency, we used a combination of data points from studies of (1) only youths (2) only adults, and (3) both youths and adults. In the third category, we retained the data points from studies that differentiated between crimes committed by youth offenders and crimes committed by adult offenders. We estimated the prevalence curves using 64 data points from 7 studies for youths and 34 data points from 3 studies for adults. We calculated the frequency curves using 110 data points from 12 studies for youths and 71 data points from 7 studies for adults.
In Figs. 3 and 4, the dashed lines represent the youth curves and the solid lines represents the adult curves. The prevalence curves in Fig. 3 show little difference in the concentration of offending among youths and adults in the population. It appears that the worst (i.e., the most criminally active) 10% of youths account for a slightly smaller proportion of their age group’s crime (about 37%) than the most active 10% of adults (about 41%). In Fig. 4, we found more concentration in the frequency of offending among the adult offenders than among the youth offenders. However, the standard errors of each curve indicate that the graphs are not substantially different from each other in terms of offending concentration (see Appendix B). Our results suggest that the prevalence and frequency of offending is similar between youths and adults.
Fig. 3 | Adult and youth offending prevalence
Fig. 4 | Adult and youth offending frequency
Males and females
Males and females differ in both the prevalence and frequency of offending. Males are more likely to offend, and those who do offend tend to commit crime with greater frequency than female offenders (D’Unger et al. 2002). This would suggest that the prevalence of offending is less concentrated among the male population and that the frequency of offending is more concentrated among male offenders. To compare male and female offending, we used a combination of data points from studies of (1) only males (2) only females, and (3) both males and females. In the last category, we retained the data points from studies that differentiated acts committed by males from those committed by females. We calculated the prevalence curves using 108 data points from 13 studies for males and 17 data points from 5 studies for females. We calculated the frequency curves using 119 data points from 14 studies for males and 35 data points from 7 studies for females.
In Figs. 5 and 6, the solid lines represent the male curves and dashed lines represent the female curves. The comparison of the prevalence curves in Fig. 5 shows some difference in the prevalence of offending among males and females in their respective populations. According to our results, the prevalence of offending is somewhat more concentrated among males. This finding contradicts our expectations, as it implies that offending is more widespread among females than among males. However, these differences are small for the males and females who are the most involved in crime. For example, the most crime-involved 10% of males account for around 66% of the crime whereas the same 10% of females account for 59% of crime. In the frequency curve comparison, we again find some difference between males and females. The frequency of offending is more concentrated among male offenders and the males who repeatedly offend are responsible for a slightly greater proportion of crime than are their female counterparts. Using the 10% of individuals who are the most involved in crime as a benchmark, this percentage of males and females account for around 42 and 37% of crime, respectively. However, given the notable disparity in numbers of studies on male and female offending, these findings must be treated with some caution, as we will discuss later in the paper.
Fig. 5 | Male and female offending prevalence
Fig. 6 | Male and female offending frequency
The United States and other countries
Comparing the distributions of offending between the United States and other countries allows us to examine crime concentration across different social, cultural, and legal contexts (Farrington 2015; Farrington and Wikstrom 1994). Using Wolfgang et al.’s (1972) definition of chronic offenders, Rocque et al. (2015b) examined the prevalence of chronic offenders in an international sample and found that they were more common in the United States and European countries than in Latin American countries. They created a proxy for the different cultural contexts by grouping the countries into five clusters based on similarities in their social welfare states. Clustering the United States with Ireland, Rocque and his colleagues found that chronic offenders comprised 10.9% of that sample, compared to 9.4% (“Western Europe”), 7.8% (“Northern Europe”), 6.2% (“Mediterranean Europe”), 5.4% (“Eastern and Central Europe”), and 4.2% (“Latin America”) of the other samples. Rocque et al. (2015b) noted that although these results suggest that the frequency of offending does vary across cultural contexts, the differences between these percentages are not large. Although they did not analyze the countries’ data individually, and the statistics cited above describe only offenders that meet their definition of chronic, Rocque et al.’s (2015b) results are still relevant to our analysis because they suggest that offending concentration does vary between nations.
We calculated the prevalence curves using 95 data points from 10 studies that used data collected in the United States and 59 data points from 5 studies that used data from other countries. We calculated the frequency curves using 170 data points from 17 studies on the United States and 118 data points from 10 non-United States studies. In Figs. 7 and 8, the solid lines represent the United States curves and the dashed lines represents the non-United States curves. The comparison of the curves in Fig. 7 shows little difference in the prevalence of offending between the United States and other countries. The 10% of people who are most involved in crime in the United States account for about 63% of the crime, whereas the same 10% in other nations account for 68% of crime, and the difference between the curves’ standard errors is also small. Thus, our results suggest that the prevalence of offending does not vary substantially between nations. The curves in Fig. 8 also show some difference in offending frequency. Offending appears to be slightly less concentrated in the United States than in other countries. Our results suggest that repeat offending is somewhat more widespread among offenders in the United States than among offenders in other nations, but the differences between the curves are small (particularly in their leftmost portions). These results seem to be consistent with the pattern in Rocque et al.’s (2015b) findings. In other words, there is some variation in the concentration of offending between nations, but these differences are not substantial, and the greater amount of spread we observe in the United States data points may be due to variations in the methods used in those studies.
Fig. 7 | United States and non-United States offending prevalence
Fig. 8 | United States and non-United States offending frequency
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