Often the most fascinating part of learning about science is the conclusions scientists (and others) draw from the evidence. Aaron Clauset, who has spent three years at the Santa Fe Institute modeling statistics of terrorism, has found that size and frequency of attack follow a power law.
the statistical distribution fits severe events like 9/11 to the same curve as more common but less severe ones that kill a dozen or so people. the pattern suggests that such rare and large events are not outliers, as was previously thought, but are somehow interconnected with the smaller attacks. the authors claim that if an underlying connection exists, then taking measures to discourage small-scale attacks might also prevent severe ones.Hat tip 3QD
As I've said before, power laws can emerge automatically from random connections between nodes; an explanation involving a power law is often a claim that no explanation is required--that the behavior is to be expected, like an equilibrium condition. It is divergence from power laws (in situations where we might expect them) that would require explanation. But of course the point of power laws is that they indicate a systematic regularity in phenomena that might otherwise be assumed to be unrelated--for example, large and small terrorist attacks. The final sentence in the above quote is the fascinating one: that not only is there a relationship between small and large attacks, it is a strong enough one that decreasing the number of small attacks should also decrease the number of large attacks.
A professor of mine once noted that there is a strong inverse correlation between the number of mules (per capita) and professorial pay within the region (that is, if one area has more mules, we would expect professors there to be paid less). Yet there is no reason to think that one causes the other--that is, killing mules will not increase professorial pay. In fact, a common cause is responsible for both: the more agricultural a state, the more mules there will be, and the lower professorial pay will be. The more urban a region, the fewer mules and the higher the pay.
It certainly seems right that large-scale terrorism should be more closely related to small-scale terrorism than are mules to payscales, but mere similarity is no guarantee.
The idea that large terrorist attacks can be prevented by dealing sharply with small terrorist attacks is an intriguing one, and it has strong similarities to a crime-reduction policy that has become popular in major US cities in recent years. The Broken Windows policy begins from the premise that most crimes are crimes of opportunity, and opportunities are more apparent in "bad neighborhoods"--those with broken windows. To reduce subway crime, then-Mayor Giuliani of New York instituted the policy of cleaning graffiti from trains on a daily basis. No train left the yard with graffiti on it. Indeed, the policy worked: graffiti on trains dropped dramatically. As did littering and turnstile jumping (although the latter probably had more to do with the complementary policy of daisy-chaining jumpers together and processing their tickets en masse with a roving paddy-wagon).
But in the larger scheme, Broken Windows has had some unfortunate side effects: many more people are incarcerated for small crimes, increasing the number of three-strikes convictions, straining the penal system, and inadvertently (one hopes) targeting the homeless and mentally ill (whose crimes are usually of the nuisance variety).
Could fighting Broken Windows Terrorism have similar unexpected consequences?