In this paper we study the causal impact of police on crime by looking at what happened to crime before and after the terror attacks that hit central London in July 2005. The attacks resulted in a large redeployment of police officers to central London boroughs as compared to outer London - in fact, police deployment in central London increased by over 30 percentin the six weeks following the July 7 bombings. During this time crime fell significantly incentral relative to outer London. Study of the timing of the crime reductions and theirmagnitude, the types of crime which were more likely to be affected and a series ofrobustness tests looking at possible biases all make us confident that our research approachidentifies a causal impact of police on crime. Implementing an instrumental variable approachshows an elasticity of crime with respect to police of approximately -0.3, so that a 10 percentincrease in police activity reduces crime by around 3 percent. |
