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Renovating abandoned houses reduces the rate of gun violence, Penn study finds

Gun crimes went up during the study, but they went up less near houses that got new doors and windows, at a cost of $5,900.

Renovating abandoned Philadelphia houses such as this one appeared to reduce the rate of gun violence nearby, a new University of Pennsylvania study finds.
Renovating abandoned Philadelphia houses such as this one appeared to reduce the rate of gun violence nearby, a new University of Pennsylvania study finds.Read morePhiladelphia Redevelopment Authority

Hammers and screwdrivers might be effective tools in preventing gun violence.

That’s the conclusion of a new study by University of Pennsylvania researchers, who measured crime rates near clusters of abandoned Philadelphia homes that were outfitted with new doors, windows, and other improvements.

Previous research has found that crime goes down when vacant houses are fixed up, but it was unclear whether the connection between those two things was more than a coincidence. To nail down whether home repairs actually prevent crimes, the Penn team tackled the question with the same rigorous approach doctors use to study a new drug: with a randomized, controlled trial.

The results left little doubt, said lead author Eugenia C. South, an assistant professor of emergency medicine at Penn’s Perelman School of Medicine.

Gun crimes increased everywhere in the city during the study period, but there was less of an increase in the neighborhood blocks surrounding renovated homes, compared to those where abandoned homes were left alone, South and her coauthors reported in JAMA Internal Medicine.

The repairs likely helped in two ways, she said: by healing the social fabric of the neighborhood and by eliminating possible hiding places for guns.

“The zoomed-out view of this is quite simply that the places and spaces around us matter for our health and well-being,” she said.

The findings come amid a continued surge of gun violence in America’s poorest big city, where officials have spent millions on antiviolence programs, in some cases with limited evidence that they work.

But in at least one case, a city-funded effort has been shown to deter crime at a fairly low cost: an ongoing program to clean and replant vacant lots. Likewise in the new Penn study, the housing repairs required a modest outlay, at an average of $5,900 per property.

The real-world experiment involved 63 clusters of abandoned homes selected at random throughout the city, each consisting of one “index” house and two to four others within a one-eighth-mile radius. The housing clusters then were divided into three groups: one to receive repairs, weeding, and trash cleanup; another to get weeding and trash pickup only; and a third to be left alone.

The repairs included installing new doors and windows on the front and sides of each house, in some cases also repairing a deteriorated facade. Workers performed follow-up maintenance on each property every 2½ months, and in 10 instances they reinstalled windows and doors that had been stolen.

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Before and after

The researchers then compared crime rates during the 18 months before and after the treatments, starting in January 2017. While crime rates rose in the areas surrounding all three types of clusters, they rose less in the vicinity of the repaired homes — in effect, representing a real reduction in crime, said Columbia University epidemiology professor Charles C. Branas, who collaborated with the Penn team.

In the areas immediately surrounding repaired houses, weapons violations were 8.4% lower than they would have been without the repairs, and gun assaults were 13.1% lower. That was roughly a reduction of one or two gun crimes per square mile every month, said Penn criminology professor John MacDonald, another study author.

The housing repairs also were associated with lower numbers of shootings, though the statistical heft of that finding was less clear. (In the clusters that got only weeding and trash pickup, no significant changes in crime rates occurred.)

The research clearly demonstrates the impact of repairs on crime rates, however limited, Branas said.

Had the authors merely tracked crime rates near houses that already were scheduled to be repaired, they could not have ruled out that any drop in crime rates was the result of other factors — say, a vigilant block captain, or a nearby store owner who hired a security guard.

Instead, by randomly selecting which clusters of houses got the treatment, the authors felt confident that any impact on crime occurred as a direct result, Branas said.

“This allowed us to really home in whether this worked or not,” he said.

Exactly how the repairs helped is less clear, but one likely reason is that criminals had fewer places to conduct illicit activity, he said. Ordinarily, the broken doors and windows in abandoned houses are covered with plywood, which easily can be peeled aside, especially once softened by rain.

“You can lift it up pretty quietly and get behind it,” he said.

Looking out for each other

Another key is that physical repairs enable healthy social interaction, said South, the faculty director of Penn’s Urban Health Lab. When decrepit houses are sealed and remediated, neighbors are more likely to go outside and connect with each other, potentially working together to head off trouble, according to past research.

“Then they can come together with their neighbors to solve problems like the trash is not picked up, or the kid down the block has been staying out too late,” she said. “Certain behaviors are just not tolerated in certain places.”

The researchers also checked to see if the repairs had simply caused criminals to take their business a block or two away, and found no such trend. The treatment seemed to have a net positive effect.

While the impact of the repairs was modest, the findings were encouraging, said Thomas Abt, a criminology researcher at the University of Maryland College Park. He was not involved with the project.

“I think we now know this works, but we also know this doesn’t work well enough to be the only strategy,” he said. “The bottom line is that paying attention to the physical environment in which crime occurs is an important piece of the overall puzzle.”

The repair work was performed by the Philadelphia Redevelopment Authority, funded by a grant from the National Institutes of Health.

Asked about the possibility of renovating more abandoned houses, Mayor Jim Kenney’s office noted that the city already spends heavily on such projects. During the fiscal year that ended June 30, the city spent $5.9 million to clean and seal 159 abandoned homes; demolish 43 others; and maintain thousands of vacant lots, spokeswoman Sarah Peterson said.

“We are grateful for the added insight into the benefits of these programs,” she said.

If the program were to be expanded, there are plenty of additional candidates for repair — with an estimated 10,000-plus abandoned houses in Philadelphia, and even greater number of vacant lots.