Taking a close look at levels of police staffing and crime rates in medium to large U.S. cities between 1960 and 2010, Aaron Chalfin and Justin McCrary of the University of California at Berkeley conclude that policing levels can have an effect on violent crime and that cities employ too few police. The researchers say that each dollar spent on police is associated with about $1.60 in reduced victimization costs.

In a paper presented today at the Association of Public Policy Analysis and Management, meeting in Baltimore, the authors say that "the precision of our estimates allows us to confirm the common and somewhat surprising finding [in earlier research] that police have more of an influence on violent crime than on property crime." The researchers compare costs and benefits of policing in various cities, finding, for example, that every dollar spent on policing in Sunnyvale, Ca., yields only 20 cents in benefits in terms of crime reduction. By contrast, every dollar spent on policing in Gary, In., yields $14 in benefits in terms of crime reduction.