Attendees flee the Route 91 Harvest country-music festival in Las Vegas, Nev., October 21, 2017. (Photo: David Becker/Getty Images)

Focus on crime ‘hot spots’ and on the tiny percentage of the population that commits most of the crime.

The violence that besieged a Las Vegas concert earlier this month is almost incomprehensible. Almost 60 died, and hundreds more were injured, as a deranged gunman rained bullets down on them from 32 stories up and 400 yards away.

Following an incident such as this, there are always two questions we must ask. First, how could we have stopped this specific tragedy from happening? And second, how can we address the broader problem of American gun violence in a way that will be both effective and consistent with the Second Amendment?


The first question is a difficult one this time. As of this writing, there is little evidence that the shooter showed signs of serious mental illness, criminal tendencies, or ties to international terrorist organizations. He passed background checks in buying at least some of his guns. If a 64-year-old multimillionaire exhibiting no warning signs is bent on mass homicide, we are unlikely to stop him before he’s achieved just that. If his weapon of choice hadn’t been a gun, it could just as easily have been a bomb (materials for which were found in his car) or a vehicle. Just last year, a vehicle attack in Nice, France, claimed even more lives than this rampage did.

There’s one gun-control measure the shooting does push into the limelight, however: The shooter possessed twelve “bump stocks,” accessories that allow semiautomatic guns to fire almost as rapidly as a fully automatic weapon. Fully automatic guns, which spray bullets continuously when the trigger is held down, are tightly regulated under federal law — indeed, it’s been illegal to sell a new one to a civilian since May of 1986, limiting the supply to the guns available before that month — but bump stocks escape these regulations because they employ different mechanisms to achieve a higher fire rate. This is clearly a loophole in the law and should be closed. These devices can dramatically increase the body count of a mass shooting but do not make a gun more useful for legitimate purposes such as self-defense or hunting.


Our second question is the more important one. Mass shootings grab our attention, but they are outliers as far as American homicide is concerned. The Las Vegas shooting may have had a double-digit body count, but 15,000 or so people are murdered each year in this country. Where mass shootings are unpredictable, other murders tend to occur in specific geographic areas and social networks. And quietly over the past two decades, criminologists, community groups, and technology companies have hit upon strategies that can reduce the bloodshed without infringing on anyone’s right to bear arms.


The fundamental insight here is that violence is incredibly concentrated. The broad demographic disparities are fairly well known: Young men, with a peak around age 20, commit murder at highly disproportionate rates, and there’s a severe racial gap, with the homicide rate for blacks about eight times what it is for non-Hispanic whites. The poor are overrepresented as well, among perpetrators and victims alike, as are people with criminal records. But the patterns get a lot more specific than that.

One study of Boston showed that over a nearly three-decade period, 74 percent of the city’s shootings occurred on less than 5 percent of its street corners and block faces.


“Hot spots” are one important concept. These are the particular neighborhoods, blocks, and intersections where crime most often occurs. Nationwide, about one-quarter of gun homicides take place in just 1,200 census tracts, which contain just 1.5 percent of the population, according to an analysis by the Guardian. Zooming in even closer, one study of Boston showed that over a nearly three-decade period, 74 percent of the city’s shootings occurred on less than 5 percent of its street corners and block faces.


Gun violence is concentrated in specific social networks as well, and “cascades” through them like a virus, a phenomenon thoroughly studied by the sociologist Andrew V. Papachristos. In one paper, he and his co-authors looked at individuals who had been arrested together in Chicago to map out criminals’ social ties and found that 70 percent of the city’s nonfatal gunshot victims “can be located in co-offending networks comprised of less than 6 percent of the city’s population.”

Jeff Asher, a New Orleans–based crime analyst, reached a similar result in work he did for his city’s police department, constructing a social network that amounted to just 0.75 percent of the population but included 26 percent of the people fatally shot in 2014. Someone from the network was confirmed present at 37 percent of all shooting incidents that year — whether as a victim, a perpetrator, or a witness — a figure that would likely rise to about half if police were able to identify all shooters. Most strikingly, one out of every 15 people in the network was present at a shooting over the course of that single year.

Data can tell us with a reasonable degree of precision not only where crime is likelier to happen but who is likelier to be involved. There are violence-reduction strategies that follow from these findings and have been tested empirically.

Essentially, data can tell us with a reasonable degree of precision not only where crime is likelier to happen but who is likelier to be involved. There are violence-reduction strategies that follow from these findings and have been tested empirically. American police departments are not ignoring those strategies completely, but there is plenty of room for improvement when it comes to funding and executing them.


One simple strategy is to police the hot spots. This has been tried and evaluated extensively, with some studies employing the scientific gold standard of randomly assigning different participating areas to be policed in different ways. (Other studies are “observational,” meaning that researchers look at crime trends in areas where certain methods are used but do not assign the methods at random. This leaves open the possibility that cities that introduce these methods also tend to make other changes that affect crime trends.) In a recent literature review, Harvard’s Thomas Abt and Christopher Winship suggested that hot-spot policing has reduced violence by up to a third in places where it’s been tried. Importantly, hot-spot policing does not appear merely to displace crime, as nearby areas do not experience crime increases.

The character of policing matters too. “Broken windows” methods — based on the concept of creating order by policing minor infractions — are effective, but they work best when the community cooperates with the police to set standards of acceptable behavior. It’s less effective for police to become an occupying force, imposing order by cracking down on every tiny violation of the law with “zero tolerance.”

Technology can help keep an eye on hot spots as well. Many cities have worked with a company called ShotSpotter to install sensors on rooftops and other elevated structures; these devices detect gunshots and notify the police of their locations. This makes the police aware of incidents that might not have been reported otherwise and allows them to analyze data on shootings.

Abt and Winship also reviewed “people-based approaches,” those premised on the fact that it is possible to identify individuals with a higher likelihood of committing violence or becoming victims of it. Easily the strongest technique of this sort, one with a track record of reducing violence by about half, is called “focused deterrence”: “the identification of specific offenders and offending groups, the mobilization of a diverse group of law enforcement, social services, and community stakeholders, the framing of a response using both sanctions and rewards, and direct, repeated communication with the individuals and groups in order to stop their violent behavior.” The idea is for authorities and community groups to pull every lever available to them to reduce the possibility of violence among those most likely to engage in it.

Such programs work and yet struggle for support. Many cities try focused deterrence only half-heartedly or let their programs fade over time. Chicago’s CeaseFire program, which deploys former gang members to help defuse volatile situations, has in recent years faced opposition from police (who don’t like working with ex-offenders) and funding cuts from the state, for instance.


There is also good evidence that when we find individuals at an elevated risk of committing violence (or committing violence again), “cognitive behavioral therapy” can help them. This is a psychological technique that works to change thinking patterns. Those undergoing it are pushed to think about how they think — and to think carefully before they act. As simple and obvious as it sounds, randomized trials show that it works to reduce youth violence. It’s a promising avenue for schools and rehabilitation programs.

To be sure, it would be entirely possible to take these measures and work harder to keep guns out of the hands of criminals. In a piece in these pages in 2015 (“Fewer Guns, Less Homicide?”; December 21), I suggested several ways to do the latter, such as requiring background checks on all gun buyers, making the gun-tracing system more efficient, improving mental-health records, and prohibiting those with misdemeanor stalking convictions from owning guns. Universal background checks are a no-go in this Congress, though the others remain possibilities.

But gun control is not the only way to reduce gun violence. It’s probably not even close to being the best way. Violence overwhelmingly occurs in specific geographic areas and among a tiny percentage of the population, both of which we can identify in advance. By focusing on these places and people, we can bring violence levels down without infringing on individual rights and picking unwinnable political fights.

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