Principal investigator: Bruno Benevit
Original title: Prison as a Criminal School: Peer Effects and Criminal Learning behind Bars
Authors: Anna Piil Damm and Cédric Gorinas
Location of the Intervention: Denmark
Sample Size: 1.928 individuals
Sector: Economics of Crime
Primary Variable of Interest: Recidivism
Type of Intervention: Pair effect
Methodology: SUR
Summary
Given the economic and social relevance of the costs of crime, understanding the factors that maintain these practices is fundamental to their mitigation. In this context, the prison incarceration process can represent a source of criminal capital, enhancing and inciting crime. This study evaluated the existence of peer effects among prisoners in Denmark, observing possible effects on the introduction of new types of crime and reinforcing previously committed types of crime. The results showed that peer reinforcement effects are strong for crimes that require planning and specific networks, such as drug crimes and robbery. In contrast, exposure to criminals of the same specialization discourages recidivism in violent crimes, such as sexual crimes and robbery.
- Policy Problem
The occurrence of crimes implies significant social and economic costs for societies, posing a major challenge for governments today. It is estimated that these crimes represent $200 billion in costs for the United States and $60 billion for the United Kingdom, where a substantial portion of these values is associated with the prison systems of these countries (DAMM; GORINAS, 2020).
However, the prison system can also bring about new adverse impacts stemming from its social dynamics. Insofar as prisoners maintain contact with each other within penitentiaries, it is plausible to assume the existence of a mechanism for transmitting new practices and improving the execution of crimes through interactions and... network among inmates. Thus, the peer effect can potentially enhance the criminal capital of these prisoners after incarceration.
Insofar as different types of crimes require distinct demands in terms of specialization and the need for coordination and networkIt is important to consider each type of crime. For example, crimes related to drugs, robbery, burglary, and receiving stolen goods may require specific capital, planning, and... networkTherefore, for the efficient allocation of resources in combating violence, as well as for greater effectiveness in the process of reintegrating prisoners into society, it is essential to understand how such social dynamics occur within the prison environment.
- Policy Implementation Context
Currently, prison practices in Denmark are characterized by a humane and adaptive approach. The Danish prison system (Danish Prison and Probation Service – The Department of Social and Penitentiary Administration (DPPS) assesses the characteristics of convicts before assigning them to institutions, considering factors such as residential proximity, medical needs, family responsibilities, or educational and work involvement. Young people aged 18 to 22 receive special attention in this process. The system differentiates prison regimes according to the individual's profile: closed prisons offer greater security, while open prisons allow greater contact with the outside environment. For young offenders, the imposition of unconditional sentences is rare, and in these cases, they are allocated to less punitive intermediate institutions. Interaction between prisoners, including activities such as classes and exercises, is widely encouraged, promoting an environment that favors social reintegration.
However, the DPPS underwent significant institutional reforms that preceded the current prison system. In 1999, a substantial reform was implemented, creating high-security sections for inmates considered highly problematic, such as gang members and outlaw motorcyclists. During the period 1994-1997, the Danish system had nine closed prisons, intended for convicts with longer sentences, and 13 open prisons, which prioritized social reintegration, allowing supervised external activities. In addition, there were smaller local prisons, often used for inmates with short sentences or awaiting trial. Furthermore, prisoners could easily interact within and between prison sections during this period, facilitating social interaction among them.
- Evaluation Details
The database used in the study combined administrative and police records covering the entire population of Denmark between 1991 and 2010. The sample was limited to young adults incarcerated for the first time between 1994 and 1997, aged 18 to 21, excluding those with prior prison interactions to avoid residual peer effects. The initial period was defined to ensure complete recording of criminal history from age 15 onwards, and the final period excluded individuals after 1997. Additionally, the analysis was terminated in 2006 due to changes in the institutional coding system. The final sample comprised 1.928 individuals.
Regarding the characteristics of the inmates, it was observed that 95% were male, and 88% were of native origin. The average age of entry into incarceration was 19 years. Approximately 10% had young children, and only 8% had completed secondary education before imprisonment. The average length of incarceration was 43 days, with two-thirds of individuals allocated to open prisons. Regarding criminal history, 53% had prior convictions for theft and robbery, 45% for violent or sexual crimes, and smaller proportions for other categories, such as drug-related crimes (11%) and weapons possession (10%). As for recidivism, 53% of prisoners received a new conviction within one year, with theft and robbery (26%) and violent or sexual crimes (8%) being the most prominent.
- Method
The study tested two hypotheses about the effects of peer interaction in Danish prisons on criminal capital: (i) introductory effects, in which individuals acquire new criminal capital by being exposed to peers specializing in different types of crime, and (ii) reinforcing effects, in which exposure to peers specializing in similar crimes strengthens prior criminal capital. To this end, the method of... was adopted. Seemingly Unrelated Regression (SUR) to estimate the probability of recidivism in specific crimes. Additionally, several model specifications were employed, considering individual and pair characteristics, such as criminal history and demographic attributes, as well as fixed effects for prison facility and criminal history.
Initially, a model was estimated to identify the probability of a young offender being incarcerated according to their type of conviction (crime committed), considering models that estimate the effects of pairs of young prisoners or of all ages in isolation. Subsequently, a model was estimated with the addition of effects associated with both types of groups simultaneously, allowing the identification of the effects of pairs on specialization and the introduction of criminal capital. Recidivism within 12 months after release was considered from seven main crime categories.
The study also conducts a series of robustness analyses adopting alternative definitions of peer groups. The authors examine potential impacts of prisoners with cultural similarities by identifying peer groups as Western and non-Western. Furthermore, groups were defined based on their type of criminal experience, seeking to identify spillover effects in the transmission of specialized knowledge. Finally, peer effects on recidivism were considered 24 months after the prisoner's release.
- Main results
The results indicated significant reinforcing peer effects for drug-related crimes and threats, both when considering all peers and when restricting the group to younger individuals. For drug-related crimes, exposure to younger peers generated additional reinforcing effects, while for threats the influence was equivalent between younger and older peers. On the other hand, introductory effects were not significant for any type of crime, suggesting an absence of influence on the diversification of criminal capital. For robberies, a significant deterrent effect was observed when considering the broad definition of peers, but this effect did not hold in other specifications. Thus, the findings reinforce the logic of criminal specialization in reinforcing effects, while introductory effects remain without empirical support.
Regarding the results on peer effects considering ethnic factors, reinforcing effects were observed among individuals with a history of drug-related crimes and threats when restricting peers to companions of the same ethnicity. The results indicated the presence of significant reinforcing effects for drug-related crimes, but not for threats. Furthermore, when comparing young offenders of the same ethnic origin with the general definition of young peers, a stronger impact on increased recidivism was identified among young drug offenders. In the analysis by criminal experience, it was identified that exposure to young recidivists intensified recidivism in drug-related crimes and threats. For vandalism and arson, recidivist peers of all ages also significantly increased recidivism rates.
Regarding the analysis considering a 24-month period for recidivism, the results corroborated the previously identified pair effects. Crimes related to drugs, threats, vandalism, and arson were reinforced, while robbery crimes showed a reduction. Furthermore, for violent crimes, a significant reduction associated with exposure to experienced repeat offenders was observed, which had not been detected in the shorter window. On the other hand, crimes such as theft and possession of weapons continued without evidence of reinforcing effects, with the exception of theft, which showed significant effects on recidivism due to exposure to young repeat offenders.
- Lessons in Public Policy
In this article, the authors investigated the existence of peer effects on the criminal capital of prisoners based on the Danish prison system, analyzing how exposure to different peer groups impacts recidivism specific to crime type. The results indicated that peers with similar characteristics, such as ethnic origin or criminal history related to the same type of crime, reinforced recidivism for crimes such as drugs, threats, vandalism, and arson. Deterrent effects were also identified for violent crimes such as robbery and sexual offenses. Introductory effects, on the other hand, were not significant. The analyses also demonstrated that the experience and age of peers intensified the effects, especially in crimes that demand greater specialization.
The results presented in this article contribute to the understanding of the factors associated with criminal recidivism. This evidence provides relevant information for strategies that seek to reduce the negative effects of coexistence among prisoners, indicating that public policies aimed at segregating prisoners based on criminal experience or specific recidivism patterns are capable of reducing recidivism rates.
References
DAMM, AP; GORINAS, C. Prison as a Criminal School: Peer Effects and Criminal Learning behind Bars. The Journal of Law and Economics, v. 63, n. 1, p. 149–180, Feb. 2020.
