Originally published in the Boston Globe Magazine on July 28, 2013.
It's not breaking news that the United States began to feel like a more dangerous place after 9/11. The Gallup Poll has reported that roughly 9 in 10 Americans have worried about future terror attacks on U.S. soil ever since. For many people, that general sense of dread got even more intense after the Boston Marathon bombings. In late April, Gallup said 51% of Americans surveyed believed another attack could happen soon, up from 38% about a year and a half earlier. Yet the reality is that we're far safer than we often feel.
In late 2012, I published a study in the journal Studies in Conflict & Terrorism that set out to estimate how many jihadi plots are in the works and how long it takes would-be terrorists to plan them. I knew that in the anxious weeks and months after a terrorist attack, it could feel as if we were under siege—as if there were bombs waiting to go off around every corner and under every subway seat. But the results of my analysis suggest otherwise: On average, at any one time there are fewer than three hidden terror plots being planned across the country.
How is it possible to count hidden terror plots? First, I reviewed hundreds of pages of indictments, criminal complaints, the testimony of FBI special agents and informants, and other court documents and reports associated with terror plots since 9/11. I then analyzed them through the lens of queueing theory, which is often used to assess the efficiency of customer-service call centers. Comparing terrorism to call centers isn't as odd as it might sound. In my research, the plots were the "customers" and the local police, FBI, or even National Security Agency (NSA) were providing the "service" of foiling them. I treated a successful plot the same way someone studying a call center would treat a customer hanging up before being helped.
For some, three terror plots will sound like a lot—any death from a terrorist attack is tragic. But I would guess that many might feel a measure of relief from the number; I know I did.
That Gallup Poll from April indicated that 40 percent of Americans worry that they or a family member could fall victim to a terrorist attack, and yet the chance is so much smaller than that. Recently, the former coordinator of the UN team that monitors Al Qaeda and the Taliban said that, between 2007 and 2011, your chances of being killed in a terrorist attack were about 1 in 20 million. You have about a 1-in-126,000 lifetime risk of being killed by lightning.
But if there are really so few plots out there, why do we invest so much money in counterterrorism? My study focused solely on jihadi plots, but over the past several years, far more people have been killed by gun violence—the lifetime odds of an American dying in a firearm assault are 1 in 340—with the Newtown school shootings and Colorado movie theater massacre two of the most terrible and visible examples. Beyond these murders, we lose many more lives to heart disease and cancer, each of which ultimately has about a 1-in-7 chance of killing you, than to terrorism.
We show our national priorities by how we spend our money: The Department of Homeland Security gets about $60 billion for its annual budget; the National Institutes of Health spends some $2 billion a year on cardiovascular research and $6 billion on cancer.
Whether this is the right sort of spending is a different discussion, but the huge outlay of money on counterterrorism is perhaps required to keep the number of successful attacks so low. In June, after Edward Snowden's revelations, the NSA's director said sweeping surveillance programs like PRISM helped disrupt more than 50 terror plots, including 10 targeting the United States. Many raised doubts about the claims—especially that the NSA played a key role in uncovering a 2009 plan to bomb the New York subway system—but the rough number of plots was comparable to what I estimated, which makes the NSA's assertions seem credible to me.
After the Marathon bombings, many questioned if warning signs were missed. This is an important concern, yet in a country as open as the United States, terrorists will sometimes succeed. Nevertheless, my research shows that at least 80 percent of all jihadi plots have been detected or deterred before anyone got hurt. This is a remarkable result. Perhaps our government's controversial counterterrorism efforts have prevented more Bostons than is commonly believed.