The Volokh Conspiracy

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More Police Officers Associated with More Black Homicides Prevented

"[E]ach additional police officer hired abates between 0.06 and 0.1 homicides [per year].... [T]he decline in homicide is twice as large for Black victims in per capita terms."


An interesting article cowritten by a UCLA Public Policy school colleague of mine, Police Force Size and Civilian Race, forthcoming from Aaron Chalfin, Benjamin Hansen, Emily K. Weisburst and Morgan C. Williams, Jr. (I quote below from the May 4, 2021 draft). I'm not an expert on this subject, but I thought it worth passing along; I'd be glad, of course, to also excerpt and link to any articles that point out flaws in this one.

The background:

While there is now a strong consensus in the academic literature that the number of police officers (McCrary, 2002; Evans and Owens, 2007; Chalfin and McCrary, 2018; Mello, 2019; Weisburst, 2019b) combined with their presence and visibility (Sherman and Weisburd, 1995; Di Tella and Schargrodsky, 2004; Klick and Tabarrok, 2005; Braga et al., 2014; MacDonald et al., 2016; Weisburd, 2016) reduces crime, whether the effect of additional law enforcement is heterogeneous across Black and white Americans remains a surprisingly open question…. Using national data on police employment for a sample of 242 large U.S. cities over a 38-year period, this research provides novel evidence on the racial differences in public safety returns to law enforcement expansion in the United States….

The homicide findings (I use curly braces below, as I often do, to indicate moved text):

We find that each additional police officer hired abates between 0.06 and 0.1 homicides [per year] …. The estimates suggest that investments in police manpower can save a life at a cost of between $1.6 and $2.7 million, far lower than common for accepted estimates of the value of a statistical life which typically exceed $7 million.

Although the total reduction in homicide is roughly equal across Black and white victims, the decline in homicide is twice as large for Black victims in per capita terms. {On a per capita basis, police force expansion has a larger effect on homicide victimization for Black civilians (0.006 0.012 homicides per 100,000 population [for each officer per year]) than for white civilians (0.002 0.008 homicides per 100,000 population). The per capita racial disparity in the effect of police force size on homicide victimization is significant … (p < 0.001).}

{On average, individuals living in the cities in our sample are 24% non-Hispanic Black, 19% Hispanic, and 49% non-Hispanic white…. In an average city-year in our data, there are 244 homicide victims, of which 138 (57%) are non- Hispanic Black and 64 (26%) are non-Hispanic white. Nationally, approximately half of homicide victims are Black—the proportion in our sample is slightly higher as we focus on large cities. In per capita terms, Black residents are approximately 4 times as likely to be the victim of a homicide compared to white residents….}

The "quality of life" arrest findings:

Next, we consider the extent to which investments in police manpower expand civilian interactions with the criminal justice system, or create "net widening" effects, focusing on differences by race in police enforcement activity. Here, we find that investments in police manpower lead to larger total numbers of low-level "quality of life" arrests, with each additional officer making 7-22 new arrests. These increases are driven by an increase in arrests for liquor violation and drug possession, with effects that imply that increases in these types of arrests are 2.5-3 times larger for Black civilians.

{[W]hile the racial disparity that we estimate is not significant at conventional levels, this test is likely conservative since, due to arrest data limitations, Hispanic arrestees are overwhelmingly classified as white for this outcome. As research indicates important Hispanic-white disparities with respect to policing outcomes (Sanga, 2009), the white estimate which includes Hispanic arrestees estimate is likely to be larger than the non-Hispanic white estimate.}

{To the extent that policymakers conclude that the costs of making large numbers of arrests for "quality of life" offenses outweigh the potential public safety benefits, we note that a number of different avenues for reform could address racial disparities in the burdens of police enforcement. Consistent with our finding that the racially disparate effects of investments in police manpower 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.}

And the findings on serious "index crimes" ("murder, rape, robbery, aggravated assault, burglary, grand larceny and motor vehicle theft"):

At the same time, we find that arrests for the most serious offenses (so-called "index crimes") fall with investments police manpower. {Consistent with the prior literature (Evans and Owens, 2007; Kaplan and Chalfin, 2019; Weisburst, 2019b), we find that each police officer abates approximately 18-24 index crimes, an estimate which implies an elasticity of index crimes with respect to police is approximately -1.1. Since larger police forces lead to reductions in index crimes, the decline in index crime arrests that we observe suggests that larger police forces reduce serious crime primarily through deterrence rather than by arresting and incapacitating additional offenders (Nagin, 2013; Chalfin and McCrary, 2017; Kaplan and Chalfin, 2019).}

On a per capita basis, the decline in index crime arrests that we observe is between 4-6 times greater for arrests involving Black suspects. This finding is consistent with the idea that police hiring has the potential to create a "double dividend" (Bratton, 2011; Cook and Ludwig, 2011; Durlauf and Nagin, 2011) for both Black and white Americans by generating reductions in both crime and arrests for serious offenses.

The authors' remarks on the broader policy implications:

Our estimates capture the historical opportunity cost of policing, by including controls that hold municipal spending fixed. In this vein, our results suggest that "de-funding" the police could result in more homicides, especially among Black victims.

Of course, reducing funding for police could allow increased funding for other alternatives. An array of high-quality research suggests that crime can, in certain contexts, be reduced through methods other than policing or its by-product, 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 (Branas et al., 2011), restoring vacant lots (Branas et al., 2016, 2018; Moyer et al., 2019), public-private partnerships (Cook and MacDonald, 2011), street lighting (Doleac and Sanders, 2015; Chalfin et al., 2019), and reducing physical disorder (Sampson and Raudenbush, 2001; Keizer et al., 2008). There is also evidence that social service-based strategies such as summer jobs for disadvantaged youth (Heller, 2014; Gelber et al., 2016; Davis and Heller, 2017), cognitive behavioral therapy (Blattman et al., 2017; Heller et al., 2017), mental health treatment (Deza et al., 2020; Jácome, 2020) and local non- profits more generally (Sharkey et al., 2017) can have important crime-reducing effects. While social service interventions are often difficult to scale (Mofiitt, 2006; Ludwig et al., 2011), the increasing number of studies which show that there are ways to reduce crime outside the deterrence channels of the traditional model of Becker (1968) is encouraging.

Whether communities should invest less in law enforcement and more in alternative strategies remains an open question, as such a material change in our society's approach to public safety has yet to be implemented at scale. Our research focuses on one crucial aspect of this policy debate—the effect of reducing police employment—an outcome which would likely result if proposals to reduce funding for municipal police departments are adopted in the future. This study provides an estimate of the historical trade-offs of investments in law enforcement and, critically, the resulting implications for communities of color.

To be sure, hiring police officers might also increase the number of blacks killed by police officers; the study notes that it "exclude[s] homicides committed in prisons or jails as well as felons killed in the commission of a crime as these are likely to fall under the legal definition of justifiable homicide" (and of course it's possible that some of the "felons killed in the commission of a crime" were actually innocent, or at least innocent of any serious crime). It's also possible that it might decrease that number, for instance by reducing the number of arrests for the serious index offenses, which may be especially likely to lead to police shootings.

But in any event, this feature is unlikely to affect the overall results of this study: The total number of blacks killed by police officers in 2020 was 241 (as compared to 457 whites), for a national average of about 0.5 per 100,000 population. Even if such shootings were positively correlated with additional police officers, that correlation is likely to be swamped by the 0.006-0.012 per 100,000 per police officer decline in homicides that the study observes. (Note that the total number of black murder victims in the U.S. was 9,913, as compared to 7,029 whites.)

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  1. This is an interesting line of posts I've seen from EV. Iirc he didn't make (m)any posts on the election fraud claims legal issues because he said he wasn't an expert in the areas. When did he become a criminologist?

    1. It's written by a colleague at UCLA. Very possibly, said colleague, looking to promote the paper, tipped him off and said "this would be interesting to put on your blog".

      1. Nah, he's done quite a few of these.

        1. Mmm, he specifically wrote:

          "An interesting article cowritten by a UCLA Public Policy school colleague of mine .... I'm not an expert on this subject, but I thought it worth passing along;"

          1. So, not an expert on election law so mum. Not an expert on criminology, here's a series of posts on the subject!

            1. Certain aspects of criminology, at least.

              Would it be impolite to notice -- let alone mention -- the string that seems to tie these curious bits together?

              Maybe it is time for some haiku . . .

            2. It's almost like he writes about whatever he wants, with his expertise on the subject being one criterion among many.

              1. Yup, isn't that exactly what Queen was pointing out? It just clearly cuts a certain way, here

                1. I don't know. It hardly seems worth pointing out.

                  Dude with blog writes about whatever he wants...

          2. Whenever police conflicts of incorrect action come up, I wonder if the trends are downward, as with all other crime the past several decades, or not.

            Apparently this is not tracked well.

            If we had this info, maybe claims of systemic racism would gain less purchase as it could be demonstrated continuous improvement as with other crime.

            But without, well...back to pure political hot air "that sounds about right".

        2. Are you suggesting EV thinks Black Lives Matter, by highlighting research that illustrates hiring more police saves a high proportion of Black Lives?

  2. Is there some formatting convention I'm unaware of with all the "{ "(curly brackets) in the quotes?

    1. Just my own practice; I've modified the post to note it, as I periodically try to do.

  3. Hardly a shocking result.

    "To be sure, hiring police officers might also increase the number of blacks killed by police officers;"

    Probably would. And most of them would be justifiably killed, as is currently the case.

    But, since even (especially?) justifiably killed by police blacks lead to riots, I wonder what the projected property damages would be?

    1. Brett Bellmore : "But, since even (especially?) justifiably....."

      My opinion? The cause of riots isn't justified or unjustified, but a belief among blacks that police officialdom, prosecutors & juries won't determine justification honestly - or punish abuses when they occur. There is some merit to that view. The Glynn County Police Department & Brunswick District Attorney were about to let the killers of Arbery slide for even their tenuous link to the local LEO community - until backed into a corner by video, that is.

      A lesser factor is low-level police harassment that reinforces mistrust in the black community. Talk to an African American and it's amazing how often they describe experiences that would be considered exceptional and infuriating by their white peers.

      An even lesser factor is the tendency of many whites to excuse any use or degree of force against a black person. I was pleased most people commenting on the National Review site applauded the Arbery verdict, but there was still a steady stream of people who used grotesquely contorted "logic" to justify the killing. This often included making the victim a criminal mastermind terrorizing the community (against all evidence, btw). Of course the comments over at Fox News were much, much worse - downright ugly, in fact. Comments at Fox tend to get ugly when there's a black person involved.

      Mistrust is the cause; I don't know the answer.

      1. You're not describing anything that could rationally be a cause for riots. You don't trust the police, so you destroy your own neighborhood? And polling says that most blacks absolutely hate the riots, so the opinions of most blacks can't be what's driving them.

        1. Brett's comment is precisely what inclines Prof. Volokh to curate his Volokh Conspiracy contributions in the manner we observe.

        2. Brett ,

          You say the riots are wrong, destructive to the black community, and opposed by a clear majority of its members. I say they reflect a distrust of police and wariness over the way officials (and large amounts of the white community) see & excuse force against blacks.

          This seems pretty obvious, but two points :

          1. There is zero contradiction between your point & mine.
          2. I agree with your points, while also holding mine.

  4. [E]ach additional police officer hired abates between 0.06 and 0.1 homicides [per year].... [T]he decline in homicide is twice as large for Black victims in per capita terms."


    BLM is essentially - pro crime

    1. The ARE pro-crime. It's a combination of BLM having Marxist revolutionary roots, "The worse, the better." and having invited into the fold urban gang members.

      1. Oooh... "marxists" and "urban gang members" !!

        Two boogeymen in one sentence! It's a two-fer!

        If you try harder, you might be able to get a trans immigrant in there too!

        1. Hell, if Brett managed to squeeze-in "trans immigrant" he'd have to go full-monty and add "Democrat" as well. But what am I saying? In Brett-World, that would probably be considered redundant....

        2. You can mock me all you like, but it doesn't change the facts.

          Black Lives Matter Co-Founder describes herself as "trained Marxist".

          Having a convicted terrorist, Susan Rosenberg, on the board of their fund raising network says something about them, too.

          And, why did you suppose BLM has no interest in black on black murder, when that's most murders of blacks?

          Because they don't really care about black lives. They just care about the cause, and it isn't a cause any decent person should join.

          1. I have the same problem here as I do when Professor Bernstein insists the Boycott, Divestment, Sanctions (BDS) movement is anti-Semitic because of something someone said at a conference forty years ago.

            In both cases we are dealing with broad diverse movements run independently in hundreds or thousands of different communities. In both cases, we are dealing with movements that do not rely on either anti-Semitism (in one case) or Marxism (in the other) to justify their beliefs. You're position, Brett, isn't just clownish, but obviously & desperately so. When I see a "Black Lives Matters" sign in someone's window, I can be comfortably sure to the 99.9 9/10th's degree that a Marxist doesn't live there. That's a problem for your position, don'tya know?

            Likewise, your "black on black murder" shtick is also thinking on a child's level. If I put a "Support Your Local Police" sticker on my bumper, that does not mean I want everyone else to go to the devil. "Save the Whales" doesn't mean I see other animals with hatred and scorn. Here's what you should ask yourself, Brett : "Why does a subject like BLM cause all the gears in my brain to freeze-up".

            You could learn a thing or two mulling that over.....

      2. You are a reprehensible. obsolete bigot, Birther Brett Bellmore.

        And a disaffected, autistic loser.

        And perhaps the precise target audience of this White, male, right-wing blog.

      3. compare (from the Russian Wikipedia article on Nikolai Leskov):
        In 1870 Leskov published the novel At Daggers Drawn, where he continued to bitterly deride the nihilists, members of the revolutionary movement forming in Russia at that time, which, in Leskov's view, coalesced with the criminal world.

  5. I remember lots of people calling for "police reform" last year talking about how US cops should behave like cops in London. Yet I do not recall any of them suggesting that US polices forces should be staffed at London Metropolitan Police levels, which is to say, with more than 200 sworn officers for each annual homicide.

    Dramatically enlarging US urban police forces (to a 200-officers-per-annual-homicide standard) would have two immediate and clear effects. The first would be a sharp decline in crime. The second would be that each cop will individually be exposed to less violence on a regular basis, with obvious knock-on effects to their psychology and behavior.

    The result, of course, would save many black lives. But we're not going to see any such enlargements, because there are no activists who actually believe black lives matter. At least not strongly enough to actually think through what would save those lives.

    1. Wow. So that's what right-wing "logic" looks like!

      Looks fun; let me try : Freezing all black people in carbonite would save many black lives. But we're not going to see that happen because there are no activists who actually believe black lives matter.

      It would be a fun parlor game to see how many other dumbass comments you could generate using the same construct. Incidentally, the city of London has one policeman per 671 residents. Using New York as equivalent, the ratio is one policeman per 150 residents.

  6. I'm confused how the authors seem to assume this is a deterrent effect, rather than a statistical artifact of the fact that if you randomly just start arresting more people, some of those people will be prevented from committing crimes they otherwise would have committed. Presumably, those likely to commit violent crimes are also more likely than the general population to engage in nonviolent crimes. The fact we could nuke the entire country and bring the murder rate down to zero if we wanted to doesn't provide us any helpful information on whether the nuclear holocaust of 330 million people is a wise or ethical policy choice.

    1. rather than a statistical artifact of the fact that if you randomly just start arresting more people

      You missed where the author said arrests also went down as police officers went up.

  7. Whether communities should invest less in law enforcement and more in alternative strategies remains an open question, as such a material change in our society's approach to public safety has yet to be implemented at scale

    I was going to type that this rendered any conclusions based on this study incomplete, but I do legit hear people on the left saying that less police is all you need for less crime. Maybe they define overly authoritarian policing as crime? I don't know; they are as silly and angry as anyone on here.

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