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Six things we’ve learned about terrorism since 9/11

There’s been a lot of research in the past 18 years. Here’s what we know.

An American flag is seen left by the engraved names of 911 victims at the edge of the north reflecting pool during ceremonies commemorating the 18th anniversary of the September 11, 2001 attacks at the 911 Memorial in lower Manhattan in New York, U.S., September 11, 2019. REUTERS/Brendan Mcdermid TPX IMAGES OF THE DAY (Brendan Mcdermid/Reuters)
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Today is the 18th anniversary of the 9/11 terrorist attacks that killed nearly 3,000 people in New York, the District and Pennsylvania. This unprecedented attack prompted many academics to study terrorism, which is violence by a subnational group to obtain a political goal through intimidation.

We’ve pulled together an exhaustive survey of the terrorism literature. Here are six things we learned about terrorism around the globe.

1. Terrorists are rational.

Politicians and the news media often portray terrorists as irrational fanatics. Scholars disagree. They see terrorists as rational and sane individuals who think strategically about how to pursue their goals, however abhorrent those goals may be. This means that they adapt and respond to government counterterrorism efforts.

For example, when the United States and other countries began installing metal detectors in airports in January 1973, the number of skyjackings plummeted. Terrorists shifted to less risky ways to take hostages, such as ordinary kidnappings. When government officials were easy targets, terrorists took advantage. In the 1970s, as governments began protecting officials, terrorists shifted to attacking businesspeople, and have since shifted further, including targeting ordinary people. The fact that terrorists are rational allows us to understand their responses to a changing environment.

2. Many counterterrorism strategies are ineffective.

Our overview shows that many counterterrorism approaches don’t work very well. Retaliatory attacks — such as the U.S. raid on Libya in 1986 in retaliation for Libya’s alleged bombing of a Berlin discotheque where many U.S. service members were injured — don’t seem to reduce future attacks by the terrorists or their sponsoring group. Terrorists actually increased their attacks immediately following the raids, advancing the schedule of already planned attacks in protest, and then attacking less for a period as they replenished spent resources.

International conventions and treaties against certain kinds of attack haven’t worked either. Technological barriers work until terrorists find innovations that can circumvent them. On the positive side, some relatively cheap actions — such as Interpol checking passports at airports — have paid off tremendously at a fairly low cost.

Countries waste resources, research shows, when they think narrowly about terrorism, considering only their own citizens. When targeted countries take defensive countermeasures, they often just displace potential attacks abroad. When governments are facing a common terrorist threat like the Islamic State, that just shifts risks and responsibilities to other targeted countries.

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3. After 9/11, terrorism hurt the world economy less than many people feared.

Unsurprisingly, small terrorism-plagued countries endure big reductions in economic growth. But on average, most nations suffer very few international terrorist attacks annually, losing little in either lives or property. As a result, terrorism has had almost no impact on economic growth, investment or consumption in the average country worldwide.

There are exceptions, of course. Tourism and foreign direct investment are affected by terrorist activities in countries or areas with significant tourism sector (e.g., Greece, Turkey, Western Europe) and foreign investments as tourists switch to other tourist destinations and investments flee for less terrorism-prone countries. However, this has had little overall macroeconomic effect, beyond shifting economic activities from more terrorism-prone economic sectors, such as tourism and airline, to other, safer sectors.

4. Poverty is not a root cause of terrorism.

Many people think that there is a straightforward relationship between poverty and terrorism. That isn’t what the data says. Disgruntled individuals in poor countries are more worried about putting bread in their mouths than using terrorism to affect politics. Rich countries, in contrast, don’t have as many people with grievances that might lead to terrorism. In terms of the number of groups and attacks, right-wing terrorism has not been a significant factor in studies to date. Research suggests that terrorism is more common in middle-income countries, both before and after 9/11, than elsewhere. For example, a study ranks 166 countries from poorest to richest based on GDP per capita and shows that the poorest 20 percent of countries accounted for about 7 percent of the domestic terrorist incidents with casualties in the world after 1993. In contrast, the countries ranked between the 20th and 60th percentile experienced 83 percent of all domestic terrorist attacks with casualties worldwide.

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5. Terrorism is most common in regimes that are neither fully democratic nor autocratic.

What’s the relationship between democracy and terrorism? There are two schools of thought. One school argues that democracies may encourage terrorism through freedom of the press, freedom of association, freedom of movement and restraints on governments — while autocracies discourage it, taking swift actions to limit terrorism. A second school disagrees, and argues that democracies may discourage terrorism by allowing political participation and protecting people’s lives.

The data suggest that neither is quite right. Terrorism is most common in political regimes that lie somewhere between democracies and autocracies. What political science calls anocratic regimes are less able than autocracies to crack down on terrorism, and unable to offer the same level of political participation as democracies. A recent article suggests that, on average, these regimes experienced far more terrorism than democracies or autocracies. For example, between 1970 and 2012, the five-year average number of transnational incidents is around 26 for Chile and 41 for Pakistan, both of which are anocracies — but just 10 for Belgium, a democracy, and 1.7 for Myanmar, an autocracy.

6. Around the world, domestic terrorism has inflicted more costs than international terrorism.

The news media often focus on international terrorist movements, which operate across countries. However, domestic terrorist campaigns, homegrown and home-directed, perpetrated far more attacks and casualties since Sept. 11, 2001.

Of course, all this differs greatly between different regions of the world. Since 9/11, as a share of domestic terrorism in the world, the regional number of domestic terrorist incidents increased in the Middle East and North Africa and decreased in Europe and North America, making the Middle East and North Africa the most terrorism-prone region in the world — hosting half of all casualties from domestic terrorism worldwide since 9/11. The same pattern is observed with regard to international terrorism. This is likely driven by two factors: the increased instability and conflict in this region, and the greater difficulty of mounting attacks in Europe and North America as security measures have increased.

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Khusrav Gaibulloev is associate professor of economics at the American University of Sharjah, United Arab Emirates.

Todd Sandler is the Vibhooti Shukla Professor of Economics and Political Economy at the University of Texas at Dallas.