As police shootings remain in the public eye and the Black Lives Matter movement demands change, vocal debate about “defunding” the police can obscure a critical point:  Most Americans, Black and white, are clear that what they want is not the end of police, but better police. What people want is police who treat civilians with respect and reduce serious crime. While most white Americans are generally satisfied with the police service they receive, among Black Americans there is considerably greater concern that the costs of policing are too high and that the benefits are not as large as they ought to be.

Do more police mean safer streets?

Are police effective in reducing crime?  Some observers have suggested that since police spend so much of their time responding to calls for service, they don’t engage in a whole lot of crime prevention.  But there is now a great deal of evidence that the presence of police officers promotes public safety.  For example, research shows that concentrating police at crime hot spots reduces serious crime in those areas and that crime levels change when police officers are reallocated in response to a terrorist attack or when they are called away from their assigned beats to deal with a serious traffic accident.

Given the Defund movement’s focus on the size of a city’s police force, it is also important to consider the effects of investments in police personnel: the number of sworn officers employed by a police department.   

What effects do changes in police force levels have on public safety and police enforcement?  And to what extent does a larger police force create racially disparate impacts for Black versus white Americans? Surprisingly, the latter question has, until now, remained unanswered. In a new paper, we look to the historical record for insights. Using national data on police employment for a sample of 242 large U.S. cities over a 38-year period, we study the effects of changes in police force size on racial differences in homicide victimization and enforcement activity in the United States. Our analysis specifically accounts for changes in total municipal expenditures over time and as such reflects the historical opportunity costs of investing those funds in an additional police officer rather than in some other item in a city’s budget.  

We find that expanding police personnel leads to reductions in serious crime. With respect to homicide, we find that every 10-17 officers hired abate one new homicide per year. In per capita terms the effects are approximately twice as large for Black victims. In short, larger police forces save lives and the lives saved are disproportionately Black lives. 

Do more police “widen the net” of the criminal justice system?

We also consider how investments in police personnel have historically affected arrest patterns for white and Black civilians. The big concern, of course, is that a larger police presence expands all manner of civilian interactions with the criminal justice system and unnecessarily fuels racial disparities in the use of incarceration. Here, the evidence suggests the impacts of investments in policing are more nuanced than they might appear.  

When cities hire more police officers, there is a decline in “index” crimes — serious offenses like robberies, aggravated assaults and burglaries that have high social costs and sometimes lead to a prison spell.  Critically, arrests for these types of crimes decline too. Why would a larger police force reduce serious crime while also making fewer arrests for that type of crime?  The answer lies in the ability of a larger police force to deter offending from happening in the first place. For example, police force expansion leads to an especially large decline in arrests for street crimes like robbery and vehicle thefts — crimes for which more cops on the street might be a particularly effective deterrent. Because fewer crimes are committed, there are fewer people to arrest. Interestingly, the decline in index crime arrests is four to six times larger for Black civilians than whites, which suggests that investments in policing are unlikely to have contributed to the massive and racially disparate growth in the scale of incarceration in the United States during the last four decades.  

Of course, prison sentences are not the only way in which investments in police may widen the net of the criminal justice system. The majority of arrests that police officers make are not for serious index crimes.  Instead, most arrests are for lower-level “quality-of-life” offenses, crimes that often do not have an identified victim but that lead to a criminal record and sometimes a jail sentence, each of which can substantially disrupt people’s lives. In some cases, these arrests, which typically involve a great deal of officer discretion, are thought to be a source of broken trust between police officers and citizens, particularly in communities that are predominantly low-income and Black. Do larger police forces lead to a proliferation of arrests for “quality-of-life” offenses and is there a racial gradient to the effects?  Our research suggests that the answer to both questions is yes, with each additional police officer hired making between seven and 22 additional arrests for such crimes. With respect to arrests for liquor law violations and drug possession, two leading arrest charges for which police usually have tremendous discretion, our research finds particularly large and racially disparate impacts, with arrests three times larger among Black civilians.  

Underpoliced or overpoliced?

Since the 1982 publication of “Broken Windows” by the political scientist James Q. Wilson and the criminologist George Kelling and the subsequent expansion of proactive, order-maintenance policing tactics in many U.S. cities, there has been considerable debate about the public safety value of making large numbers of arrests for low-level “quality of life” crimes.  While the majority of early research suggested that today’s misdemeanor arrests prevent tomorrow’s felony crimes, a litany of more recent scholarship calls that conclusion into question.  There continues to be an active debate about the public safety benefits of low-level arrests. But given that police have benefits as well as costs, a natural question to ask is whether U.S. cities are underpoliced or overpoliced.  

Our research suggests that this question cannot be answered without appealing to strong normative beliefs about how to weigh the costs and the benefits of policing. But it is also fair to wonder whether we should be asking a different question. Instead of asking whether we are hiring the right number of police, we can also ask whether policing can become better and more precise — preserving the critical public safety benefits that policing can deliver to disadvantaged communities while minimizing the costs. In other words, can we invest in the most productive elements of policing, which improve public safety, without unnecessarily exposing larger numbers of people to the harmful effects of the criminal justice system?

The upshot is that we have not fully explored strategies that combine a relatively heavy police presence with a relatively hands-off approach to enforcing minor offenses. Skeptics might argue that such strategies are impossible, but we disagree. In fact, a number of reforms could address racial disparities in the burdens of police enforcement while also maintaining critical improvements in public safety. Consistent with our finding that the racially disparate effects of investments in police personnel are particularly large for drug possession arrests, the decriminalization of the possession of small amounts of drugs may be a particularly promising avenue for reducing racial disparities. Similarly, prior research suggests that racial disparities might be reduced by efforts to recruit a larger number of Black or female police officers as well as by the application of “precision policing,” a suite of strategies in which police effort is reallocated more intensively towards the small number of individuals in a community who are driving the most socially costly types of offending, in particular, gun violence.  

Policing isn’t the only answer — but tread carefully

Of course, reducing funding for police could allow increased funding for alternatives. Indeed, an array of high-quality research suggests that crime can be reduced through methods other than policing or its byproduct, incarceration. Among the many alternatives to police for which there is promising evidence are place-based crime control strategies such as increasing the availability of trees and green space, restoring vacant lots, public-private partnerships in the form of business improvement districts, street lighting, and reducing physical disorder. There is also evidence that social service-based strategies such as summer jobs for disadvantaged youth, cognitive behavioral therapy, mental health treatment, and local nonprofit formation focused on building strong communities more generally can have important crime-reducing effects.  

While an increasing number of promising studies show that there are ways to reduce crime outside of the traditional deterrence channels like police and prisons, it bears mentioning that social service interventions are often difficult to scale and may take time to pay dividends.  

Ultimately, what will happen if a city decides to substantially reallocate resources away from police and towards social services? No one knows the answer to this question since it has never been done before.  To this end, we note that all of the studies evaluating the effectiveness of social service interventions implicitly hold police funding and behavior fixed, just as studies of investments in policing hold funding for social service-based strategies fixed.  

Our research provides novel insight into a fundamental policy lever generally used to address homicide victimization and other serious crime — police employment. We show that police force expansion can lead to significant improvements in racial disparities related to public safety, at a time in which the role of law enforcement is under intense public scrutiny. At the same time, our research also documents the consequences of policing practices that disproportionately expose disadvantaged communities to the criminal justice system.  

Aaron Chalfin is an Assistant Professor of Criminology at the University of Pennsylvania and a research affiliate at the University of Chicago Crime Lab.

Benjamin Hansen is the W.E. Miner Professor of Economics at the University of Oregon and a National Bureau of Economic Research Affiliate.

Emily Weisburst is an Assistant Professor of Public Policy at the Luskin School of Public Affairs at the University of California, Los Angeles.

Morgan C. Williams, Jr. is an Assistant Professor/Faculty Fellow at the New York University Robert F. Wagner Graduate School of Public Service.