Terrorist Attacks and Comparable Risks, Part 2

John Adams argues that our irrationality about comparative risks depends on the type of risk:

With "pure" voluntary risks, the risk itself, with its associated challenge and rush of adrenaline, is the reward. Most climbers on Mount Everest know that it is dangerous and willingly take the risk. With a voluntary, self-controlled, applied risk, such as driving, the reward is getting expeditiously from A to B. But the sense of control that drivers have over their fates appears to encourage a high level of tolerance of the risks involved.

Cycling from A to B (I write as a London cyclist) is done with a diminished sense of control over one's fate. This sense is supported by statistics that show that per kilometre travelled a cyclist is 14 times more likely to die than someone in a car. This is a good example of the importance of distinguishing between relative and absolute risk. Although 14 times greater, the absolute risk of cycling is still small -- 1 fatality in 25 million kilometres cycled; not even Lance Armstrong can begin to cover that distance in a lifetime of cycling. And numerous studies have demonstrated that the extra relative risk is more than offset by the health benefits of regular cycling; regular cyclists live longer.

While people may voluntarily board planes, buses and trains, the popular reaction to crashes in which passengers are passive victims, suggests that the public demand a higher standard of safety in circumstances in which people voluntarily hand over control of their safety to pilots, or to bus or train drivers.

Risks imposed by nature -- such as those endured by those living on the San Andreas Fault or the slopes of Mount Etna -- or impersonal economic forces -- such as the vicissitudes of the global economy -- are placed in the middle of the scale. Reactions vary widely. They are usually seen as motiveless and are responded to fatalistically - unless or until the threat appears imminent.

Imposed risks are less tolerated. Consider mobile phones. The risk associated with the handsets is either non-existent or very small. The risk associated with the base stations, measured by radiation dose, unless one is up the mast with an ear to the transmitter, is orders of magnitude less. Yet all round the world billions are queuing up to take the voluntary risk, and almost all the opposition is focussed on the base stations, which are seen by objectors as impositions. Because the radiation dose received from the handset increases with distance from the base station, to the extent that campaigns against the base stations are successful, they will increase the distance from the base station to the average handset, and thus the radiation dose. The base station risk, if it exist, might be labelled a benignly imposed risk; no one supposes that the phone company wishes to murder all those in the neighbourhood.

Less tolerated are risks whose imposers are perceived as motivated by profit or greed. In Europe, big biotech companies such as Monsanto are routinely denounced by environmentalist opponents for being more concerned with profits than the welfare of the environment or the consumers of its products.

Less tolerated still are malignly imposed risks -- crimes ranging from mugging to rape and murder. In most countries in the world the number of deaths on the road far exceeds the numbers of murders, but far more people are sent to jail for murder than for causing death by dangerous driving. In the United States in 2002 16,000 people were murdered -- a statistic that evoked far more popular concern than the 42,000 killed on the road -- but far less than the 25 killed by terrorists.

This isn't a new result, but it's vital to understand how people react to different risks.

Posted on April 13, 2010 at 1:18 PM • 12 Comments


HJohnApril 13, 2010 1:59 PM


Seems that's how it should be. There is a huge difference between someone who murders another and one who takes someone's life in an accident (with varying degrees of culpability based on the level of negligence or carelessness or wrecklessness involved).

NickApril 13, 2010 2:01 PM

Don't forget about the need to stop future events. I'm not sure exactly where this idea falls on the "rational" scale, but we cannot forget that in many of these classifications of risk, beyond our feeling of control over that risk, there is also the feeling of needing to prevent further occurrences.

Although deaths from murder and rape occur less often than road deaths, it is viewed as easier to punish murder to prevent people from deciding murder is acceptable in the future (thus increasing its rate) than it is to prevent random car accidents.

Terrorism also falls into this category. Because some of these attacks are so large, people feel that we need to react strongly, even though (statistically) our risk is small, b/c if we don't, then more will occur in the future, and all of a sudden the risk won't be small any more. But by then, it might be too late to effectively stop.

anonApril 13, 2010 3:00 PM

I'm still not convinced that it makes sense to compare terrorist attacks to, say, cycling deaths. Cycling, driving, flying, etc. fatalities are all accidents. Even if the vehicle manufacturers and transit operators are willing to entertain "acceptable" risk limits, the purpose is to provide service, not danger. On the other hand, the terrorists' purpose is to kill/hurt/scare.

DanielApril 13, 2010 4:17 PM

James. But I think that's the point. The problem with articles like Adams's is that they skip over the really important thing. Namely, that we as human beings do a terrible job of understanding what risk actually is. Risk is not only absolute and relative; it's always and inherently comparative. People are not being stupid when they listen to stories; they are simply reducing the risk of looking stupid by being out of touch with their peers.

Objective risk can't be dissociated from subjective values. Academics do it all the time but it's a fools errand. Telling the public that bicycling is less risky when it takes into account the health benefits from regular cycling is wasted breath on a populace that (a) doesn't like cycling and (b) isn't obsessed by longevity.

Marian KechlibarApril 14, 2010 2:14 AM

In fragile countries, political violence has potential to grow quickly into an all-out civil war or genocide. See Bosnia + Lebanon + Rwanda for relatively recent examples.

Iraq stopped just at the edge of the abyss, and is not in safety yet.

That is why people, at least those who live in politically fragile countries (admittedly USA is not one of them) have good reason to worry about political violence in general, even though the death record for one selected year is very low. Because it can grow fast from 3 casualties a year into 3000 a day. Obviously, road risks can't grow like this.

drscroogemcduckApril 14, 2010 5:53 AM


if 2000 people are murdered and 2000 people die in car crashes then if we are punishing purely based on harm done then if the murderers spend 20,000 days in prison then the dangerous drivers should also be spending 20,000 days in prison (or equivalent).

the problem is the people who are causing deaths from dangerous driving aren't getting equivalent punishment to murders because dangerous driving has a lower probability of causing death than murdering. this would be ok if we were also punishing people who were dangerous driving that weren't causing deaths enough to make up the difference. it is possible that fines+other punishments are already making up this difference but i'm not sure.

also, there is the case that some 'dangerous driving' is actually an efficient breach and is socially optimal. by using punishments like prison we lower social utility. however, since most benefits of 'dangerous driving' accrue to the dangerous driver punishments like fines can push us towards the optimal level of 'dangerous driving'.

hwKeitelApril 14, 2010 9:18 AM

cars and cyclist.

it depends on how you drive. like an idiot, normal, or careful (on two, on four, or with no wheels). you are not the only one to make a failure. maybe you have the control over your vehicle, but the person in the slow car in front of you has problems with your speed or with his car.
always be prepared for the failures of other people. that's not about fear, it is the realistic valuation of the abilities of the other road users.

life is interaction. so you have to find a level to interact with people around you.

hwKeitelApril 14, 2010 9:47 AM

i've a problem comparing (car) accidents with murder or terror. the first are accidents (besides suicides etc.) and the other not.
it is a famous comparison, but i don't like it. it's not objective, it's like comming up with the Nazis. comparing car crashes and murder does not support any argumentation.

in Germany there was a news about a guy having 1800 points in Flensburg. if you make i big driving mistake (driving drunk, speeding, etc.), you get a point in Flensburg, a fine, etc.. as soon as you have to many, they take your driving licence for a while (or you have to make the idiot test). i don't know exactly where the limit is (somthing around 15 points). this guy was driving without a driving licence (you get 6 points) and got caught 300 times! now he moves to prision.

is the radio a believable source?

NobodyApril 14, 2010 4:56 PM

But if the point of prison is to deter murderers by showing them the punishment then it would seem to make sense to deter, drunk, careless or speeding drivers in the same way.

The reason we don't punish dangerous drivers is that we punish people in direct relation to how far they are from us.
When faced with a death by dangerous driving - the jury thinks 'that could have been me' and is lenient.

The same reasoning is behind the huge payouts awarded against large corporations and why minorities get convicted.

Kjetil KjernsmoApril 19, 2010 2:18 PM

I'm a climber, and I've taken a few rather high risks. One thing that once amazed me was that after I had climbed Norway's third highest mountain, a mountain of considerable difficulty, so that only good climbers go there, I was the only one who would use the seat belts on the bus home... I was the one who by most are thought to take silly risks, yet, I was the only one who would use a security measure that had near-zero costs...

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Photo of Bruce Schneier by Per Ervland.
