Policymakers should

When seeking to create policies to deal with any hazard that threatens human life and to expend funds, the single most important question to ask at the outset is also one that is almost never put forward when formulating policy about terrorism. It is not “Are we safer?” but “How safe are we?”

In the United States from 1970 through 2015, the odds of an American being killed by a terrorist (of any sort) were 1 in 4 million per year. Those low numbers lead to the question posed shortly after 9/11 by risk analyst Howard Kunreuther: “How much should we be willing to pay for a small reduction in probabilities that are already extremely low?”

Questions like Kunreuther’s are too rarely asked within the U.S. government. A 2010 assessment by a committee of the National Academy of Sciences concluded that domestic counterterrorism funds were expended without serious analysis of the sort routinely required in other areas of government, or even the sort carried out by the Department of Homeland Security (DHS) itself for natural hazards. The committee could not find “any DHS risk analysis capabilities and methods” adequate for supporting the decisions made.

Extensive and transparent efforts to evaluate counterterrorism expenditures in the United States are long overdue. Instead, policymakers have maintained their alarmist perspectives and perpetuated vast and hasty increases in spending on homeland security.

It is possible to apply standard cost‐​benefit and risk‐​analytic procedures of the sort called for by the National Academy committee. These procedures have been developed, codified, and increasingly used as an aid in responsible decisionmaking for decades — or in some respects, for centuries. And they have been applied to a wide variety of hazards, including ones that are highly controversial and emotive, such as pollution, chemical power plant accidents, and exposure to nuclear radiation.

One of these approaches involves the concept of “acceptable risk,” a phrase that has been almost completely neglected in discussions about counterterrorism expenditures. Risks tend to be deemed acceptable if they cause death in fewer than 1 in 1 million or perhaps 1 in 2 million cases per year. Hazards that fall into the unacceptable range (traffic accidents, for example) should generally command the most resources, whereas less should be spent to combat hazards in the acceptable range (drowning in bathtubs, for example).

If the threat that terrorism presents to human life in the United States is — in that sense — “acceptable,” then efforts, particularly expensive ones, to further reduce its likelihood or consequences are unjustified. Spending on more smoke alarms, tornado shelters, car safety, and other measures would save far more lives.

Another approach is to calculate how many lives domestic counterterrorism expenditures would need to save to be justified. Following widely applied procedures, a study for DHS concluded that the best estimate of the value of a saved human life for homeland security measures would be about $15 million. Under that stipulation, domestic counterterrorism spending ($72 billion across the government in 2016, according to the Office of Management and Budget) would be worthwhile if it prevented some 4,800 terrorism deaths in the country each year. That figure seems to be very high: even with the San Bernardino and Orlando tragedies included in the count, Islamist extremist terrorists in the United States have killed about seven people a year since 9/11.

Yet another approach is a full cost‐​benefit analysis. This analysis could seek to determine, for example, how many terrorist attacks the increase in expenditures since 9/11 would have had to deter, disrupt, or protect against to be justified. The number turns out to be quite high: 150 attacks like the Boston Marathon bombing each year — about one every other day; or 15 attacks per year like the one in 2005 on the London transportation system — more than one a month; or about one 9/11 attack every three years. Similarly, methods of protecting a standard office building are cost‐​effective only if the likelihood of a sizable terrorist attack on the building is a thousand times greater than it is at present. Assessed individually, some security measures, such as hardening airline cockpit doors, do seem to be cost‐​effective whereas others, like the Federal Air Marshal Service, don’t.

A defender of current spending might argue that the number of deaths from terrorism is low primarily because of the counterterrorism efforts. But, although those measures should be given some credit, it is not at all clear that they have made a great deal of difference.

To begin with, the people prosecuted on terrorism charges in the United States do not seem to be all that capable. The RAND Corporation’s Brian Jenkins’ assessment is apt: “their numbers remain small, their determination limp, and their competence poor.” Left on their own (and absent help by infiltrating operatives from the Federal Bureau of Investigation), it seems likely that few, if any, of them would have actually been able to cause much damage.

In addition to those prosecuted on terrorism charges, authorities have encountered a considerable number of people who seem to be aspirational terrorists. Lacking enough evidence to convict these individuals on terrorism charges, prosecutors have levied lesser ones to put, or send, the perpetrators away. However, these people are even less likely than those charged with terrorism to be willing and able to carry out attacks. Because they receive short sentences, many have been released; but few, if any, have even tried to commit a terrorist attack since release. It is clearly not a very determined bunch.

Finally, we are often told that security measures deter terrorists. Some targets — airliners and military bases, for example — may indeed have been put out of reach by security measures. But no dedicated terrorist should have much difficulty finding other ones if the goal is to kill people, destroy property, or get attention. Suitable targets are everywhere.

These considerations are based on history, and there is no guarantee that the frequencies of the past will persist into the future. Things could become worse. However, it is up to those who hold such a view to explain why they think terrorists will suddenly get their act together and become capable of massively increasing their violence in the United States.

The terrorist threat as it currently exists does not justify the hundreds of billions that have been spent on it since 9/11. If, as is likely, policymakers will not undertake cuts, they should at least require DHS to conduct more rigorous cost‐​benefit analyses of its programs.

Suggested Readings

Brooks, Risa A. “Muslim ‘Homegrown’ Terrorism in the United States: How Serious Is the Threat?” International Security 36, no. 2 (Fall 2011): 7–47.

Friedman, Benjamin H., Jim Harper, and Christopher A. Preble, eds. Terrorizing Ourselves: Why U.S. Counterterrorism Policy Is Failing and How to Fix It. Washington: Cato Institute, 2010.

Jenkins, Brian Michael. Stray Dogs and Virtual Armies: Radicalization and Recruitment to Jihadist Terrorism in the United States since 9/11. Santa Monica, CA: RAND Corporation, 2011.

Mueller, John, and Mark G. Stewart. Chasing Ghosts: The Policing of Terrorism. New York: Oxford University Press, 2016.

—. “Responsible Counterterrorism Policy.” Cato Institute Policy Analysis no. 755, September 10, 2014.

National Research Council of the National Academies. “Review of the Department of Homeland Security’s Approach to Risk Analysis.” Washington: The National Academies Press, 2010.