Working Paper: CEPR ID: DP9889
Authors: Matthew Lindquist; Yves Zenou
Abstract: We study peer effects in crime by analyzing co-offending networks. We first provide a credible estimate of peer effects in these networks equal to 0.17. This estimate implies a social multiplier of 1.2 for those individuals linked to only one co-offender and a social multiplier of 2 for those linked to three co-offenders. We then provide one of the first empirical tests of the key player policy in a real world setting. This policy defines a micro-founded strategy for removing the criminal from each network that reduces total crime by the largest amount. Using longitudinal data, we are able to compare the theoretical predictions of the key player policy with real world outcomes. By focusing on networks for which the key player has disappeared over time, we show that the theoretical predicted crime reduction is close to what is observed in the real world. We also show that the key player policy outperforms other reasonable police policies such as targeting the most active criminals or targeting criminals who have the highest betweenness or eigenvector centrality in the network. This indicates that behavioral-based policies can be more efficient in reducing crime than those based on algorithms that have no micro-foundation.
Keywords: crime; crime policies; key player; peer effects; social multiplier; social networks
JEL Codes: A14; K42; Z13
Edges that are evidenced by causal inference methods are in orange, and the rest are in light blue.
| Cause | Effect |
|---|---|
| Cooffending with one person (K42) | Increase in individual's propensity to commit crime (K42) |
| Increase in individual's propensity to commit crime (K42) | Social multiplier effect of 1.2 for individuals linked to one cooffender (C31) |
| Increase in individual's propensity to commit crime (K42) | Social multiplier effect of 2 for those linked to three cooffenders (C92) |
| Implementing key player policy (Z22) | Predicted crime reduction of 38% (K42) |
| Key player policy (E61) | Outperforms other strategies in crime reduction (K42) |