By any reasonable measure, we’re far too apprehensive about terrorism and expend far too many resources and sacrifice far too much liberty defending against its risks. But there are smart ways and dumb ways to make that point.
Nate Silver, responding a few days ago to one of my posts, demonstrates the former:
Over the past decade, according to BTS, there have been 99,320,309 commercial airline departures that either originated or landed within the United States. Dividing by six, we get one terrorist incident per 16,553,385 departures.
These departures flew a collective 69,415,786,000 miles. That means there has been one terrorist incident per 11,569,297,667 mles flown. This distance is equivalent to 1,459,664 trips around the diameter of the Earth, 24,218 round trips to the Moon, or two round trips to Neptune.
Assuming an average airborne speed of 425 miles per hour, these airplanes were aloft for a total of 163,331,261 hours. Therefore, there has been one terrorist incident per 27,221,877 hours airborne. This can also be expressed as one incident per 1,134,245 days airborne, or one incident per 3,105 years airborne.
There were a total of 674 passengers, not counting crew or the terrorists themselves, on the flights on which these incidents occurred. By contrast, there have been 7,015,630,000 passenger enplanements over the past decade. Therefore, the odds of being on given departure which is the subject of a terrorist incident have been 1 in 10,408,947 over the past decade. By contrast, the odds of being struck by lightning in a given year are about 1 in 500,000. This means that you could board 20 flights per year and still be less likely to be the subject of an attempted terrorist attack than to be struck by lightning.
For those not inclined to view the video, one of Sully’s readers helpfully summarizes the latter:
In 2008 there were 34,017 deaths (and nearly 100,000 major injuries) related to automobile accidents in the United States. Terrorists would have to blow up 113 Boeing 777-200s each year in order to kill that many people! That is, they’d have to blow up all but six of the 777-200’s (which hold 301 people in a 3-tier international setup) currently owned by American Airlines, United Airlines and Continental Airlines (together they own 119 777-200s) and would have to do so every single year, which is probably faster than they can be built.
And yet there is hardly any talk of defending the American people from their Buick!
Yes, Americans willingly accept the risks that come with driving in order to accrue the substantial benefits. But we drive far, far more often than we fly. That’s why commercial airplane crashes always make the news whereas automobile accidents tend to make it on our radar screens only when they involve professional golfers being chased by supermodels wielding golf clubs.
Furthermore, it’s not entirely unreasonable to react differently to random acts of fate than willful acts of malice. People willingly build houses near the ocean even though the probability of eventual damage from a hurricane is exceedingly high. But they nonetheless lock their doors, buy alarm systems, and fund police forces to minimize the risk of burglary.
Still, as Matt Yglesias observed yesterday,
People understand that flying is way safer than driving, right? Making it more of a pain in the name of “safety” will kill people.
So, while factoring in the public’s justly having more concern about human-caused dangers than random ones is reasonable, there must be limits.