In 2007, Princeton University economist Alan Krueger published a short book, What Makes a Terrorist, based on three lectures he gave in Britain debunking many of the myths about terrorism. Now he has published a 10th anniversary edition with a new prologue and updated material. What distinguishes his work from many others on the subject is his empirical approach: he looks carefully at the data.

The three chapters of the book are titled, “Who Becomes a Terrorist? Characteristics of Individual Participants in Terrorism,” “Where Does Terror Emerge? Economic and Political Conditions and Terrorism,” and “What Does Terrorism Accomplish? Economic, Psychological, and Political Consequences of Terrorism.” In each chapter, he draws on data to answer those questions, and what he finds is striking:

  • International public opinion surveys find that support for terrorism is higher among those who are more highly educated and have higher family income. One striking statistic comes from a survey of 1,318 Palestinians in the West Bank and Gaza Strip: 86.7% of merchants and professionals, versus “only” 73.9% of the unemployed, supported armed attacks against Israeli targets.
  • Terrorists “are more likely to be well educated and less likely to come from impoverished backgrounds” than the populations from which they come.
  • International terrorists—Krueger never defines the term but, in context, he means (and he confirmed this by email) those who engage in terrorism against foreign targets, whether in their own or in other countries—tend to come from countries whose governments suppress civil liberties and political freedom.
  • There is no connection between a country’s income per capita or illiteracy rate, on the one hand, and the number of international terrorists from that country, on the other.
  • Terrorists’ preferred targets tend to be wealthy countries whose governments respect civil liberties and political freedom rather than poor countries with repressive governments.
  • Distance matters; that is, international terrorists and foreign insurgents tend to come from countries that are geographically close to the countries they target.
  • For their acts to have the desired effects, terrorists who use conventional methods of terrorism “need the media to propagate fear.”

Understanding terrorism / To discuss terrorism, you first need to define it. Krueger characterizes terrorism as “premeditated, politically motivated violence.” He notes that although this characterization doesn’t exclude state-sponsored terrorism, his goal is to consider “substate organizations and individuals with the intent of influencing an audience beyond the immediate victims.”

In context, his winnowing down to non-state actors makes sense because what many people would like to understand is who the substate actors are and what motivates them. I think I understand, for example, the vengeance motive that led the U.S. government, early after its entry into World War II, to send Lt. Col. Jimmy Doolittle and his squad’s airplanes to firebomb the Japanese mainland. But what many people aren’t entirely sure of is what causes various non-state actors to attack the targets they choose in, say, the United States. Krueger doesn’t answer everything we might like to know, but he does give some answers and is careful not to go far beyond what he can extract from the data.

On the lack of a connection between terrorism on the one hand and poverty and low education level on the other, Krueger, besides looking at his assembled data, makes a big-picture empirical point: “If poverty and inadequate education were causes of terrorism, even minor ones, the world would be teeming with terrorists eager to destroy our way of life.” In fact, he notes, uneducated poor people are particularly unlikely to participate in any political processes, terrorist or otherwise. They are too busy trying to make a living.

When we think of terrorism, many of us think of Muslims. University of Chicago political scientist Robert Pape, who gathered data on every known case of suicide terrorism between 1980 and 2003, found little connection between it and Islamic fundamentalism. Krueger cites Pape and reports on his own study, co-authored with David Laitin, that found similar results for terrorism in general. Krueger and Laitin looked into whether a country with a high percentage of Muslims is more likely to be a home to terrorists than a country with a high percentage of Christians. They found no significant difference.

What motivates terrorists? Krueger found that “countries that occupy other countries are more likely to be targets of terrorism.” That certainly makes sense. Interestingly, though, he also found that countries that are occupied are only “slightly more likely to be perpetrators of terrorism.” Of course, countries can’t perpetrate terrorism. Krueger is clearly referring to terrorists and identifying them by the country they came from. And many terrorists seem to come from third countries, rather than occupier or occupied countries.

Inflating the risk / How serious a problem is terrorism? Krueger’s table of relative risks shows that the answer is “not very.” An American’s lifetime risk of being killed by a terrorist, calculates Krueger, is 1:69,000. Compare that to the 1:88 chance of being killed in a motor vehicle accident and the even more serious 1:7 risk of dying from cancer and 1:4 risk of dying from heart disease. Based on other risks he shows in his table, he writes, “In 2005 the average American’s chance of being killed by a terrorist was much less than his or her chance of being killed by lightning or in an airplane crash.”

People often respond to this by pointing out that, with terrorism, someone is actively trying to kill others, whereas with the other risks, fatalities “just happen.” While that certainly should affect our moral evaluation—lightning is amoral, while a terrorist is virtually certain to be immoral—it should not affect one’s evaluation of relative risks. Krueger doesn’t address this response, probably because he sees it as the red herring that it is. But his table of risks implicitly answers the argument. He shows that an American’s lifetime probability of being murdered is 1:240, which is 287.5 times the probability of being killed by a terrorist. In both cases, the killing is intentional.

Given the small risk of terrorism, Krueger is right to decry government officials’ pronouncements that hype the threat. He reports that in July 2007, Michael Chertoff, then secretary of homeland security, told the Chicago Tribune of his “gut feeling” that al-Qaeda might attack the United States that summer. His reasoning was that “summertime seems to be appealing to them.” But Krueger, using the government’s own data, found no summer spike in al-Qaeda terrorist attacks between 2004 and 2006. He found 10 attacks in the winter, 13 in the spring, nine in the summer, and seven in the fall.

He notes that in the summer of 2007, someone had brought his evidence to the attention of the Department of Homeland Security. Did DHS then say, “Oops, our bad?” Dream on. Instead, DHS spokesman Russ Knocke responded, “If any doubt lingers in his [Krueger’s] mind about activity in spring and summer months in recent years, he need only ask the families of victims from London, Madrid, and 9/11.” In his book, Krueger has a great comeback: “Evidently Mr. Knocke does not think it important to consider the victims of terrorist attacks that occurred in winter and fall.”

More than a decade before giving these lectures, Krueger was the chief economist in President Bill Clinton’s Department of Labor; after giving these lectures, he went on to become chairman of the Council of Economic Advisers (CEA) under President Barack Obama. His experience in government doesn’t seem to have led him to the same skepticism about government competence that I had in my two early-career stints at the CEA.

He does find fault, quite justifiably, with the important statistical errors issued by the State Department under President George W. Bush’s secretary of state, Colin Powell. For instance, a major report on world terrorism in 2003 was supposed to cover the entire year, but the last terrorist attack it listed in the appendix was on November 11. This made no sense, argues Krueger, because on November 15, there were attacks in Turkey on two synagogues, the British consulate, and a British bank. Krueger’s solution is for the State Department to have its own statistical agency, but he doesn’t express any overall skepticism about the government’s competence in dealing with terrorism.

At one point, he notes that terrorists may be “motivated by some grievance concerning American activity in the Middle East, such as the presence of American troops in the Persian Gulf and American support of autocratic regimes friendly to the United States.” He concludes that we “have to confront their grievances.” But he adds, “And we may not want to confront their grievances.” His solution instead, which he admits is unlikely to be “an important part of the solution,” is to have the government—presumably he means the U.S. government—control the content of education that people in other countries receive.

He never suggests that government officials be fined or even fired for misreporting facts. But he doesn’t have the same tolerance for private-sector actors. He writes, “Perhaps the FCC could keep track of inaccuracies in reporting on terrorism and fine media outlets if they repeatedly make mistakes.” It is certainly true that the media hype terrorism and that that has bad effects. But his confidence in proposing that a government agency be given the power to fine those who are exercising their freedom of speech is breathtaking.

While I recommend the book overall, I point out one thing that is missing. In a well-referenced book, nowhere does Krueger mention an article that makes many of the points he does about relative risks and about how the main damage from terrorism comes not from terrorism per se, but from its provoking destructive government policies. The article I’m referring to, published over a year before Krueger’s 2006 lectures, is Ohio State University political scientist John Mueller’s “A False Sense of Insecurity” in these pages (Fall 2004).