Terrorism and Statistics

There was an interesting editorial in Sunday’s New York Times about the anxiety produced by terrorism and people’s general inability to deal rationally with said anxiety. All kinds of interesting stuff that I didn’t know or hadn’t thought about. Nassim Nicholas Taleb, a professor at UMass Amherst, writes that risk avoidance is governed mainly by emotion rather than reason, and our emotional systems tend to work in the short term: fight or flight; not fight, flight, or look at the evidence and make an informed decision based on the likely outcomes of various choices. Dr. Taleb points out that Osama bin Laden “continued killing Americans and Western Europeans in the aftermath of Sept. 11”: People flew less and drove more, and the risk of death in an automobile is higher than the risk in an airplane. If you’re afraid of an airplane hijacking, though, you’re probably not thinking that way. It would be interesting to do a causal analysis of the effect of the September 11 terrorist attacks on automobile deaths (maybe someone already has?).

6 thoughts on “Terrorism and Statistics

  1. I am not sure about the status of that factoid about cars being more dangerous than aeroplanes. Cars have a lot of accidents, but most of these occur in towns, on journeys for which aeroplanes are obviously not substitute. People also often make the comparison on the basis of deaths per mile travelled, which is a metric that penalises the car for having a fairly constant hazard rate throughout the journey rather than a dangerous bit at the start, a dangerous bit at the end and a very long relatively safe bit in the middle. On a deaths-per-journey basis for journeys over 100 miles, I am not at all sure that the relative risk would significantly favour the aeroplane. In particular, by grounding private planes (which really are surprisingly dangerous) for an extended period, Osama might have saved a few lives.

  2. (btw, I don't know what the NYT is playing at with that byline; Taleb probably does teach the odd risk-mangement class at Amherst but his main job is managing a financial firm).

  3. There was an investigation on this topic in Psychological Science (Gigerenzer, G. (2004). Dread risk, September 11, and fatal traffic accidents. Psychological Science, 15, 286–287).

    Here's the abstract:

    "People tend to fear dread risks, that is, low-probability, high-consequence events, such as the terrorist attack on September 11, 2001. If Americans avoided the dread risk of flying after the attack and instead drove some of the unflown

    miles, one would expect an increase in traffic fatalities. This hypothesis was tested by analyzing data from the U.S. Department of Transportation for the 3 months following September 11. The analysis suggests that the number of Americans who lost their lives on the road by avoiding the risk of flying was higher than the total number of passengers killed on the four fatal flights. I conclude that informing the public about psychological research concerning dread risks could possibly save lives."

    I wrote a letter to the journal to warn against a potential ecological fallacy and proposed to investigate this question in a case-control design or the like, but the editor didn't like to publish the letter.

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