Since 9/11, terrorism has loomed large as a pervasive security issue. Has terrorism really reached an unprecedented level, or has sensational news coverage inflated the threat? Is terrorism a danger in some places more than others?

To start answering those questions, the first step is to determine what actually counts as a terrorist attack.

Defining terrorism is a challenge, requiring researchers to make a number of decisions when classifying incidents as terrorist attacks. 

The Global Terrorism Database, operated by START at the University of Maryland, is the largest public database on terrorist violence. It is a compilation of every terrorism incident on record since 1970 and includes information detailing the location of each attack, the group responsible, the type of weapon used, the number of casualties, and more.

START’s definition of a terrorist incident is based on three criteria; an attack must meet at least two of those to be listed in the START database:

  • The violent incident is designed to meet a political, economic, religious, or social goal.
  • It’s meant to coerce, intimidate, or convey another message to a broader audience.
  • It targets civilians and is not an act of war.

Terrorism is, by definition, frightening. When fear drives decision-making, the resulting policies can easily respond to the wrong threats. Collecting global data on terrorist attacks and deaths allows researchers to confirm or challenge claims about the threat of terrorism, which can be inflated by politicians or media coverage. The data collected by START reveals, among other things, that the vast majority of terrorist attacks don’t make international headlines, and half of terrorist attacks claim no lives. A comprehensive look at terrorism allows policymakers to develop strategies that take into account the real nature of terrorist attacks: the groups responsible, the methods they use, the grievances that drive them, and the places they act.

What trends emerge from the data? 

Zeroing in on the United States reveals that terrorism-related deaths have increased since 2012 after a decade of remaining relatively low. The spike in 2012 was driven by a slight increase in terrorist attacks but mostly, in fact, by a few particularly lethal mass shootings. Because the overall volume of terrorist attacks in the United States is low relative to other parts of the world, one attack with a significant number of casualties can have an outsize effect on the data. The 2017 shooting in Las Vegas, for example, killed fifty-eight people, causing the trend line to shoot up. And while the upward trend is worrying, data on terrorism-related deaths and attacks occurring in the United States, versus in other parts of the world, makes clear that Americans face a relatively low threat from terrorism.

Terrorism Violence in the United States

Globally, terrorist violence went up significantly between 2002 and 2014.

This trend began to reverse itself in 2014, which was the deadliest year on record in terms of terrorism-related deaths. Since 2014, both the number of terrorist incidents and resulting deaths have actually declined—a trend not always clear from media coverage—but both remain at historically high levels. For example, terrorist attacks in 2017 were more than twice as common as they were in 1992, the peak year for an earlier wave of terrorist violence. And 2017 saw nearly eight times more terrorism-related deaths than 2001.

Global Terrorist Violence

Both the 2014 peak in terrorist violence and the subsequent decline are the result of a stark reality: the vast majority of terrorism is driven by a few particularly lethal groups operating in areas of conflict in the Middle East and Africa. 

Since 2001, 99 percent of all terrorism-related deaths have occurred in countries embroiled in conflict, such as Afghanistan, Iraq, and Syria, or have high levels of political terror (meaning extrajudicial killings, torture, and imprisonment without trial), like Nigeria. In 2013, more than 80 percent of deaths from terrorism took place in Iraq, Afghanistan, Pakistan, Nigeria and Syria.

The 2014 spike in terrorist attacks and deaths came from a few extremely lethal groups operating in areas of conflict, namely, the Islamic State and Boko Haram. The Islamic State, Boko Haram, the Taliban, and al-Shabaab, an al-Qaeda affiliate, are responsible for more than half—54 percent—of all terrorism-related deaths caused by known groups between 2002 and 2017.

The Four Deadliest Terrorist Groups, 2002–2017

Percentage of Terrorist Deaths, 2002–2017

Logically, then, the decrease in terrorist violence since 2014 is the result of the containment of the deadliest terrorist groups in the places where they are most active. The Islamic State has lost all of its territory in Iraq and Syria, and starting in 2015 Nigeria launched a military campaign against Boko Haram.

The data illustrates this correlation. As conflict has died down, so has terrorism: deaths from terrorism and battlefield deaths have climbed and fallen together in Afghanistan, Iraq, Nigeria, Pakistan, Somalia, and Syria. Analyzing these two trends, it’s clear that the vast majority of terrorism is used as a tactic within an armed conflict or against repressive political regimes.

Though the Islamic State no longer controls territory in Iraq and Syria, it remains the deadliest terrorist organization in the world.

It has maintained this grim title mainly because attacks outside Iraq and Syria by individuals inspired by the Islamic State have been increasing. Between 2013 and 2016, forty-two countries faced Islamic State–related terrorist attacks. These attacks, in places like Australia, France, Germany, and Sri Lanka often receive intense media coverage, which contributes to the heightened perception of the threat terrorism poses today. In fact, in 2017, 98 percent of Islamic State attacks and deaths occurred in the Middle East and North Africa; almost 90 percent of attacks occurred in Iraq alone.

Terrorism is undoubtedly one of today’s defining global challenges. Understanding how data is collected and what it reveals about where terrorism looms largest, can help put threats in perspective.

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