[ExI] Probability of being affected by terrorism [WAS Re: Mass transit]

[Richard Loosemore]

Anders Sandberg wrote:
> Richard Loosemore wrote:
>> Keith Henson wrote:
>>> As usual, airtight reasoning from Anders.
>>
>> Uh, not so fast.
> Thanks Keith, and you're right, Richard. :-)
> 
> In fact, I have partially redone the calculations more carefully and 
> found a few minor issues. I will post them on my blog a bit later (right 
> now I am sitting on the London-Oxford bus, hardly the best place for 
> getting probability theory stringent). Basically, it turns out that the 
> risk of being harmed from a single-victim feral is a bit larger in small 
> groups (avoid elevators!) because of the smaller pool of potential 
> victims. And for power-law distributed terrorism there is a situation 
> where there exist a finite most dangerous group size for a given 
> probability of people being terrorists and for the damage exponent. But 
> they hardly change my core conclusions.
> 
>>
>> Terrorism (or feral actions, if you will) are often not designed to 
>> target the individuals they hurt directly, but to target the 
>> perceptions of the majority of society.
> 
> Yup. In many ways this is a good thing, since terrorists do not seem to 
> maximize lethality.
> 
>>
>> So, please redo the calculations and include the probability of "side 
>> effects" such as these, which utterly dwarf the direct effects.
>>
>> (Hint:  correct answer is that the probabilities cannot be computed in 
>> any meaningful way).
> 
> Depends on whether you are a subjectivist or not about probabilities. I 
> see no problem with saying that the risk of being affected is = P(me 
> affected|side effects) P(side effects|terrorism) P(terrorist act). The 
> probabilities are going to be subjective estimates, largely set by 
> experience and messy, unreliable intuition. A more elaborate model 
> taking real world structure into account might even give better 
> estimates, but it will still merely be a best guess. This entirely OKand 
> rational as long as correctly update probabilities as I get new 
> evidence; I might wish for the certainty of mathematics or firm 
> empirical data, but in a world of unknowns and black swans this is what 
> we have to make do with.
> 
> Actually, let's play around a bit with our assumptions and see what 
> happens. I think we have a pretty good model of terrorism being power 
> law distributed with exponent -2.5. The amount of effect a terrorist 
> action has depends on 1) where it happens, 2) how big it is, 3) how 
> outrageous it is. Who can name this week's terrorist actions without 
> googling? They all happened in the usual far-away countries we tend to 
> skim over in our news reading, and they happened to people we do not 
> know. Conversely, 911 was an unusually big terrorist event - it is an 
> outlier in the data, and the effect was of course amplified by happening 
> in a major developed country and in an outrageous fashion (not all 
> tragedies are equal). I would model this by saying the effect probably 
> scales with the size X as X^k, where k>1. The proper thing would be to 
> actually check the amount of coverage different terrorist actions have 
> got as a function of their sizes, building a proper probability model. 
> Finally, let's make a guesstimate of how the event effect influences the 
> chance of it influencing me. I can see an argument for a threshold 
> effect (small ones rarely matter, big ones have a high likeliehood): a 
> simple model would be P(affected|effect)=(effect}^p where p is another 
> exponent > 1, and we clamp the result to [0,1]. Now, putting all this 
> together we get P(me affected|event size = X)=CX^(k+p-2.5) where C is 
> the normalization factor.
> 
> This crude estimate already tells us something interesting. Unless 
> k+p<2.5 (which is unlikely, since both are by assumption > 1) there is 
> going to a be a critical terrorism size that affects everybody. This is 
> in many ways the terrorist sweet spot: it is hard to make big X attacks, 
> but if you reach a sufficient size you will get global effects - it 
> actually doesn't pay making bigger attacks. If k+p<2.5 big attacks do 
> not pay: too hard to do, and there is insufficient reaction to them. So 
> other forms of "politics by other means" are needed. So if we want to 
> reduce terrorism it might be interesting to consider *ignoring* it to a 
> certain extent - overreactions play into the hands of terrorists (and 
> anti-terrorists, of course).
> 
> (OK, this is as far as I could get between London and Oxford...)

I think the only problem now is that whereas your first calculation was 
relatively tight (absent minor errors), you have allowed yourself such a 
degree of wiggle-room in the assumptions built into your new calculation 
of the side effects of terrorism that your eventual conclusion was that 
the range of probability-of-being-affected could easily have an upper 
bound of 1.  (I.e. everybody would be affected).

Which was kind of what I said, but in words... :-)

The important factors, as always, lie elsewhere (cf my post on the 
IEET.org website last week).  What matters most is actually the damping 
factor, not the terrorism itself.  The damping factor for U.S. terrorism 
targets is currently Fox "News" and its legislative branch  .... and 
that, of course, is a negative damping mechanisms (i.e. amplification).

Conclusion is:  forget the terrorists and target the terrorism 
amplification mechanisms.



Richard Loosemore