Explosives. Arson. Guns. Driving into a crowd of people.
These are the most common tools that terrorists use to inflict fear and destruction on an unwitting public.
But a new study suggests that these violent methods, while all horrific, are not equally deadly.
In a research letter published Friday in JAMA Internal Medicine, investigators report that although guns were used in fewer than 10% of terrorist attacks worldwide between 2002 and 2016, they were responsible for more than half the resulting deaths.
The new work was led by Dr. Robert Tessler of the Harborview Injury Prevention and Research Center in Seattle.
To better understand the deadliness of different types of terrorist attacks, he and his team consulted the Global Terrorism Database maintained by the National Consortium for the Study of Terrorism and Responses to Terrorism at the University of Maryland.
The group defines a terrorist attack as the "use of illegal force and violence by a non-state actor to attain a political, economic, religious or social goal through fear, coercion, or intimidation." (Based on this definition, the mass shooting in Las Vegas on Sunday night that killed 58 people and injured nearly 500 would not qualify as a terrorist attack.)
The database uses a combination of machine learning and manual review to gather information from more than 1 million daily media reports published in 80 languages around the world. For each attack, information on the location, type and number of fatalities is provided.
For this study, Tessler and his colleagues looked at data from 2,817 terrorist attacks in the United States, Canada, Western Europe, Australia and New Zealand between 2002 and 2016.
Of these, 85.3% were in Western Europe, and 11.7% were in the U.S.
Explosives were used in 49% of all attacks, followed by arson (36%), firearms (9.2%) and vehicles that plowed into crowds of people (5.4%).
An additional 3.1% of attacks were labeled "miscellaneous." (Single attacks can include multiple weapons, resulting in a total over 100%.)
The proportion of terrorist attacks involving firearms was highest in the United States compared with other countries. Between 2002 and 2016, 20% of all terrorist attacks in the U.S. involved firearms.
The Netherlands had the next-highest rate of terrorist attacks with guns: about 14%.
The authors suggest that policymakers take this work into account when considering future legislation to protect citizens from terrorism.
MORE IN SCIENCE