Scientists at Iowa State University conducted a study that calculated the probability of a mass shooting in every state and in public places like shopping malls and schools, Study Finds reports. The scientists say the new method they’ve put together for quantifying the risk of a mass shooting in specific places may one day help security officials make informed decisions when it comes to planning for emergency events.
To conduct this study, Iowa State associate professor Cameron MacKenzie and his doctoral student, Xue Lei, applied a number of statistical methods and computer simulations to a database of mass shootings from 1966 to 2020 — originally put together by The Violence Project. For reference, The Violence Project technically defines a “mass shooting” as any incident in which four or more victims are killed by a firearm in a public place. The U.S. has experienced at least one mass shooting every year since 1966.
The Violence Project also includes the percentage of mass shootings across different types of locations. The research team used that data specifically to calculate the odds of a mass shooting in nine different types of public locations (a restaurant, school, workplace, house of worship, etc.) in two states (California and Iowa). Importantly, mass shooting odds were also estimated for the two largest high schools in both of those states.
They found that the states with the greatest risk of a mass shooting are also the most populous: California, Texas, Florida, New York, and Pennsylvania. Together, those states account for close to 50 percent of all mass shootings. Some states, like Iowa and Delaware, have never experienced a mass shooting.
The annual risk of a mass shooting at the largest California high school is roughly 10 times greater than the risk at the largest high school in Iowa. The amount of mass shootings in the U.S. has increased by approximately one shooting every 10 years since the 1970s.
MacKenzie notes that the chances of a mass shooting at a specific location depend heavily on one’s exact definition of the term. For example, unlike The Violence Project, The Gun Violence Archive defines a mass shooting as four or more individuals shot, injured, or killed in any location, not just a public location. Consequently, The Gun Violence Archive has collected copious data on shootings in both public and private locations as well as targeted shootings (gang shootings, etc).
When researchers opted to apply data provided by The Gun Violence Archive to their models, the predicted number of annual mass shootings came out to be nearly 100 times more than a forecast based on The Violence Project’s data.