This paper puts forth an explanation of the recent escalation of violent crime in Colombia. The paper considers three implicit models that isolate different types of externalities among criminals. In the first model criminals make crime more appealing to nearby residents by congesting the law enforcement system and hence lowering the probabiliTY of punishment. In the second model the interaction of career criminals and local crooks speeds up the diffusion of criminal know-how and criminal technology. In the third model the daily contact of youth with criminal adults and criminal peers results in the erosion of morals and hence in a greater predisposition toward crime. The paper shows that a myriad empirical evidence -both statistical and anecdotal- lends support to the previous models in general and to the congestion-in-law-enforcement model in particular.
