Northwestern University sociology professor Andrew Papachristos conducted a study which found that gun violence is an epidemic concentrated within what he called “networks.” His study of Chicago’s gun violence, which was included in Northwestern’s 2018 Impact Report, showed that 90 percent of shootings occurred within a single, large network of people consisting of 6 percent of the city’s population.

A lot of Papachristos’ work over the past decade has been based on network science, which is an approach that tries to model networks, or the connections between people, and how it affects what they feel, think and do.

“What we know is that networks affect who you vote for, what you buy, who you marry, whether or not you get a raise, whether or not you have a good idea, whether or not you get a disease. And so a lot of what my work has done over the last decade is apply that logic to crime and violence, particularly gun violence,” Papachristos said.

Using this approach, Papachristos has applied network science to develop a model to help predict specific outcomes. In the area of gun violence, he wants to use his research to determine who is going to get shot and when in order to implement intervention tactics to reduce this violence.

Through his research, both in this study and studies he conducted in about a dozen other cities, he made three main findings. One, gun violence is concentrated more severely within social networks such as a disadvantaged neighborhood. Two,exposure to gun violence increases the likelihood for it to affect someone and, three, it is temporally and spatially contagious, meaning that once gun violence occurs, it creates a cascade of violence through social spaces that diminishes over time.

In his most recent Chicago study, he observed the physical gun circulation in the city to determine the ripples it has in social networks. By using data of guns confiscated by the police, the study found that individuals were only 2.5 handshakes away from obtaining a gun.

Papachristos said that these results can be used to determine policy initiatives regarding illegal gun use and intervening in the immediate risk of gun injury or trauma. Since gun violence in your network increases your likelihood of experiencing it, he recommends implementing more rapid response outreach and trauma services to mitigate these effects in more at-risk neighborhoods.

“There’s a role for police in gun violence prevention and it should be limited, but this sort of approach I’m advocating for is more holistic. If you have a public health model, you have a whole range from primary care to tertiary care to emergency care and police are just one very specific element,” Papachristos said.

Papachristos is now researching police accountability within social networks and believes that this application of network science will only continue to expand the understanding of sociological issues.