While the dataset included mass shootings, and many notable mass shootings took place at schools, the majority of these events did not take place on school campuses. Rather, most school-associated homicides, like other juvenile homicides, tend to be gang-related, drug-related, or otherwise linked to criminal activity or interpersonal disputes. The shooting occurs at a school because of the opportunity for attack.
In examining the data, there were distinct periods of time when school shootings were elevated, for example 1993 and 1994 and 2008-2010. This suggested that an outside factor could be considered a cause for the increases. Examining these periods of time, it became clear there was a congruence between periods of increased unemployment and more frequent episodes of school shootings.
The unemployment rate became a particular interest since it uniquely captures the difficulties faced by older students who struggle to get a job or who experience joblessness in their families. Unemployment is related to lowered self-esteem, diminished status and detrimental behavior, such as drug and alcohol abuse.
There is also evidence that minors whose parents are affected by high unemployment are more likely to believe that they will have difficulty getting jobs. Therefore, gun violence at schools may be a response, at least in part, to the lost hope for improving economic opportunities.
In addition to looking at unemployment, other proxies for economic insecurity include the home foreclosure rate, which has a significant financial and emotional impact on families, and consumer confidence.
The research also focused on the six cities with the most gun violence at schools: New York City, Detroit, Chicago, Memphis, Los Angeles, and Houston. As seen on the national and regional level, increases in the number of school shootings correlated with periods of higher unemployment in these cities.