What is the Evidence on Increasing Department Size?
Increasing department size is listed under “What do we need to know more about?” on our Review of the Research Evidence.
Weisburd and Eck (2004) argued that increasing the size of police departments generally has not proven to be an effective way of reducing crime.The problem here is that it is very difficult to accurately measure the impact of increasing department size on crime, in part because departments often increase in size as a result of increases in the crime rate. Policing research tends to suggest that what cops are doing on the street matters much more than department size per se. We do know from data on police strikes that not having police at all tends to lead to crime increases (e.g. Makinen & Takala, 1980), but it is less clear how to calculate the crime control value of hiring one additional police officer.
Marvell and Moody (1996) note that in 78 prior assessments of the link between number of police and crime from 36 studies, just 14 found a significant beneficial impact of more police. However, they also detail the difficulties of disentangling the relationship between crime and number of officers. Their own analyses suggest a significant impact of police levels on crime, particularly at the city level. Evans and Owens (2007: 183) point to improvements of recent studies but conclude “Even with these recent efforts, there is scant evidence that more police reduce crime.”
More recent studies and reviews have come to somewhat conflicting results, again suggesting the lack of ability to reach strong conclusions. A review of the evidence by Bradford (2011), for example, argues that many of the studies suffer from methodological limitations, but that there is some evidence that increasing police agency sizes may have some beneficial impact on reducing property crime. In contrast, an analysis of 242 cities by Chalfin and McCrary (2018) focused on correcting errors that can exist in the Uniform Crime Report employment data, found a generally greater impact of officer numbers on violent crime than property crime.
As noted above, the 1994 Crime Control Act provided millions in federal funding to local police agencies in an effort to add 100,000 police to the streets. Studies of the impact of grants from the COPS Office on crime are conflicting. The Government Accountability Office’s (2005) assessment of COPS grants suggested the program was responsible for about 5 percent of the 26 percent drop in total crime between 1993 and 2000. Other studies found inconsistent results, some suggesting a relationship between the grants and crime declines (see Evans & Owens, 2007; Zhao, Scheider, & Thurman, 2002) and others finding little or no impact of the grants on crime rates (see Muhlhausen, 2001; Worrall & Kovandzic, 2007). Based on these findings from studies of both the number of police in general and police hired by COPS grants, we find it difficult to reach strong conclusions about the relationship between levels of police and crime.
Evidence-Based Policing Matrix
There are currently no studies on increasing department size in the Evidence-Based Policing Matrix.
Seattle Police car image courtesy of Flickr user Atomic Taco and used under a Creative Commons license.