Offenders perform most of their offenses alone but might be willing to participate in a co-offense. The majority of co-offenses involve two people. Property crimes: High co-offending rates, small group sizes Often instrumental; involve physical help and information sharing Larger groups reduce individual profit Violent crimes: Low co-offending rates, large group sizes Arise from social dynamics, diffusion of responsibility, and heightened group violence Female offenders commit fewer crimes than males but rely equally on co-offending Females may be coerced into co-offending by partners Often learn about new crime opportunities from male co-offenders Young offenders are more likely to co-offend and in larger groups Greater peer exposure during adolescence Co-offending decreases with experience Average group size Co-offenders prevalence Co-offense prevalence Age group Database search Domain knowledge Existing reviews 110 included studies Crime type Sex Property Violent Male Female Youth Adults ~5000 studies Legend Pooled prevalence of co-offenses: 0.29, 95% CrI: (0.22–0.35) based on a total of 45,973,445 offenses Pooled prevalence of co-offenders: 0.50, 95% CrI: (0.43–0.56) based on a total of 3,459,133 offenders 0.39, 95% CrI: (0.32–0.47) 0.27, 95% CrI: (0.21–0.34) 0.56, 95% CrI: (0.49–0.63) 0.44, 95% CrI: (0.37–0.51) 0.53, 95% CrI: (0.45–0.61) 0.54, 95% CrI: (0.46–0.62) 0.71, 95% CrI: (0.65–0.77) 0.41, 95% CrI: (0.34–0.48) Pooled average group size: 2.73, 95% CrI: (2.63–2.84) 2.67, 95% CrI: (2.41–2.88) 2.79, 95% CrI: (2.66–2.93) 2.83, 95% CrI: (2.64–3.01) 2.54, 95% CrI: (2.08–2.90) 2.88, 95% CrI: (2.59–3.18) 2.66, 95% CrI: (2.38–2.91) Quantifying Criminal Collaborations A systematic review and Bayesian meta-analysis of co-offending characteristics Ruslan Klymentiev, Dayle Harvey, Luis E. C. Rocha & Christophe Vandeviver “Co-offending is a key ingredient to high rates of criminality.” (McCord and Conway, 2002, p.25) Inclusion criteria At least one descriptive measure Disorganized crimes "Co-offending" as co-presence at a crime event or co-arrest Measures of interest Prevalence of co-offenses Prevalence of co-offenders Average group size Longevity of co-offending groups Network analysis measures Additional variables Crime type (Property, Violent, Other, All) Sex (Male, Female, Both) Age group (Youth, Adults, All) Bayesian analysis All scripts and data used in this study are available via the Open Science Framework platform at https://doi.org/10.17605/OSF.IO/RUF9K Klymentiev, R., Harvey, D., Rocha, L. E. C., & Vandeviver, C. (2025). A systematic review and Bayesian meta-analysis of co-offending characteristics. Nature Human Behaviour, 9(10), 2135–2152. https://doi.org/10.1038/s41562-025-02244-z Co-offending is a term used to describe the act of two or more individuals collaborating to commit an offense (Weerman, 2003). Reiss (1988) argues that studying co-offending is vital for understanding the causes of crime and designing prevention policies, as arresting one offender may not reduce crime when others can continue offending, replace them, or recruit new partners. However, the full scale of co-offending remains unknown. McCord, J., & Conway, K. P. (2002). Patterns of juvenile delinquency and co-offending. In E. Waring & D. Weisburd (Eds.), Crime and Social Organization (1st ed., pp. 15–30). Routledge. Reiss, A. J. (1988). Co-offending and criminal careers. Crime and Justice, 10, 117–170. https://doi.org/10.1086/449145 Weerman, F. M. (2003). Co-offending as social exchange: Explaining characteristics of cooffending. The British Journal of Criminology, 43(2), 398–416. BACKGROUND METHODOLOGY RESULTS REFERENCES DISCUSSION CODE & DATA ACKNOWLEDGMENTS CITATION This work was supported by the Research Foundation – Flanders (FWO) (grant numbers G017122N, C.V. and L.E.C.R.; W001625N, L.E.C.R. and C.V.), Belgian Federal Science Policy Office (grant number B2/223/P3/BeForIntel, C.V.) and Special Research Fund (grant number 2024/01/709, L.E.C.R.). Artwork credit: Natalia Hromanchuk ✉ Correspondence:
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