The problem of terrorism is getting worse worldwide.
Where? Since when? And by what measure?
Historically speaking, terrorism is rare, and mass-casualty terrorist attacks rarer still. In terms of the sheer number of individual attacks committed in, for example, the United States and Europe, terrorism has actually declined significantly from its 1970s peak. (At the time, left-wing and right-wing terrorist groups were active throughout Europe; the United States had a particular problem with Puerto Rican nationalists.)
The U.S. has been especially safe from terrorism since September 11; the highest-casualty terrorist attack in the country since then occurred in San Bernardino in 2015, and yielded a death toll of 14 people. Overall the death toll from terrorism in the United States from 2004 to 2014, the most recent decade for which data was available, was 56, far below the toll of the 1990s, when 218 people died in terrorist attacks in the United States, 168 of them killed in the Oklahoma City bombing of 1995.
Still, the number of terrorist incidents worldwide, and the number of fatalities they cause, has jumped alarmingly in recent years, driven largely by events in just five countries—Iraq, Nigeria, Afghanistan, Pakistan, and Syria. As the State Department reported based on figures through 2014, “The number of terrorist attacks in 2014 increased 35 percent and total fatalities increased 81 percent compared to 2013,” partly due to the increasing lethality of some individual attacks. “In 2014, there were 20 attacks that killed more than 100 people, compared to two such attacks in 2013.”
On the other hand, no one really agrees on the definition of “terrorism”—there’s a reasonable degree of consensus that terrorism consists of politically motivated attacks by non-state actors, but it’s not clear where “terrorism” ends and acts of “insurgency” or “civil war” begin. As John Mueller and Mark Stewart pointed out recently: “[V]irtually any violence perpetrated by rebels in civil wars is now being called terrorism. ... Before 9/11, terrorism was, by definition, a limited phenomenon. ... If terroristic violence became really sustained and extensive in an area ... the activity was generally no longer called terrorism, but rather war or insurgency.” They concluded: “The post-9/11 conflation of insurgency with terrorism makes it seem that the world is awash in terrorism, something that stokes unjustified alarm outside war zones, where terrorism remains a quite limited hazard.”
Even with this expansive definition, less than 7 percent of violent deaths worldwide are the result of terrorism; as Micah Zenko pointed out in Foreign Policy last year, “Citizens of several Central American and Caribbean countries are still more likely to be the victim of homicide than Iraqis or Syrians are from terrorism.”