DP4421 Who's Who in Crime Networks: Wanted - The Key Player

Author(s): Coralio Ballester , Antoni Calvó-Armengol , Yves Zenou

Publication Date: June 2004

Keyword(s): social networks , crime , centrality measures , key group , policies

JEL(s): C72 , K42

Programme Areas: Public Policy

Link to this Page: www.cepr.org/pubs/dps/DP4421.asp

Criminals are embedded in a network of relationships. Social ties among criminals are modelled by means of a graph where criminals compete for a bounty and benefit from local interactions with their neighbours. Each criminal decides in a non-cooperative way how much crime effort they will exert. We show that the Nash equilibrium crime effort of each individual is proportional to their equilibrium Bonacich-centrality in the network, thus establishing a bridge to the sociology literature on social networks. We then analyse a policy that consists of finding and getting rid of the key player, that is, the criminal who, once removed, leads to the maximum reduction in aggregate crime. We provide a geometric characterization of the key player identified with an optimal inter-centrality measure, which takes into account both a player’s centrality and their contribution to the centrality of the others. We also provide a geometric characterization of the key group, which generalizes the key player for a group of criminals of a given size. We finally endogeneize the crime participation decision, resulting in a key player policy, which effectiveness depends on the outside opportunities available to criminals.