The same elements of psychology lead people to exaggerate the likelihood of terrorist attacks: Images of terrifying but highly unusual catastrophes on television—such as the World Trade Center collapsing—are far more memorable than images of more mundane and more prevalent threats, like dying in car crashes. Psychologists call this the “availability heuristic,” in which people estimate the probability of something occurring based on how easy it is to bring examples of the event to mind.
As a result of this psychological bias, large numbers of Americans have overestimated the probability of future terrorist strikes: In a poll conducted a few weeks after September 11, respondents saw a 20 percent chance that they would be personally harmed in a terrorist attack within the next year and nearly a 50 percent chance that the average American would be harmed. Those alarmist predictions, thankfully, proved to be wrong; in fact, since September 11, international terrorism has killed only a few hundred people per year around the globe, as John Mueller points out in Overblown. At the current rates, Mueller argues, the lifetime probability of any resident of the globe being killed by terrorism is just one in 80,000.
This public anxiety is the central reason for both the creation of DHS and its subsequent emphasis on showy prevention measures, which Schneier calls a form of “security theater.” But that raises a question: Even if DHS doesn’t actually make us safer, could its existence still be justified if reducing the public’s fears leads to tangible economic benefits? “If the public’s response is based on irrational, emotional fears, it may be reasonable for the government to do things that make us feel better, even if those don’t make us safer in a rational sense, because if they feel better, people will fly on planes and behave in a way that’s good for the economy,” Tierney told me. But the psychological impact of DHS still has to be subject to cost-benefit analysis: On balance, is the government actually calming people rather than making them more nervous? Tierney argues convincingly that the same public fears that encourage government officials to spend money on flashy preventive measures also encourage them to exaggerate the terrorist threat. “It’s very difficult for a government official to come out and say anything like, ‘Let’s put this threat in perspective,'” he told me. “If they were to do so, and there isn’t a terrorist attack, they get no credit; and, if there is, that’s the end of their career.” Of course, no government official feels this pressure more acutely than the head of homeland security. And so, even as DHS seeks to tamp down public fears with expensive and often wasteful preventive measures, it may also be encouraging those fears—which, in turn, creates ever more public demand for spending on prevention.
Michael Chertoff’s public comments about terrorism embody this dilemma: Despite his laudable efforts to speak soberly and responsibly about terrorism—and to argue that there are many kinds of attacks we simply can’t prevent—the incentives associated with his job have led him at times to increase, rather than diminish, public anxiety. Last March he declared that, “if we don’t recognize the struggle we are in as a significant existential struggle, then it is going to be very hard to maintain the focus.” If nuclear attacks aren’t likely and smaller events aren’t existential threats, I asked, why did he say the war on terrorism is a “significant existential struggle”? “To me, existential is a threat that shakes the core of a society’s confidence and causes a significant and long-lasting line of damage to the country,” he replied. But it would take a series of weekly Virginia Tech-style shootings or London-style subway bombings to shake the core of American confidence; and Al Qaeda hasn’t come close to mustering that frequency of low-level attacks in any Western democracy since September 11. “Terrorism kills a certain number of people, and so do forest fires,” Mueller told me. “If terrorism is merely killing certain numbers of people, then it’s not an existential threat, and money is better spent on smoke alarms or forcing people to wear seat belts instead of chasing terrorists.”