Fiddler’s Green

| Gabriel |

Matt at Permutations links to a critique of the famous zombie epidemiology paper. The original paper was your basic diffusion model, which assumes spatial homogeneity, and as people like to do to these kinds of models, the critique relaxes that assumption. Specifically the new model assumes a gradient of areas that are relatively favorable to humans, perhaps because of resource stocks, terrain that’s easily defensible with a rifle, etc. The new model then finds that the equilibrium is not total apocalypse, but a mixed equilibrium with substantial depopulation with few zombies and a relatively large number of humans.

Being both the world’s foremost expert on the sociology of zombies and a diffusion guy, I feel obliged to weigh in on this. The new model adds a parameter of “safe areas” but assumes that “safeness” is exogenous. However, if the Romero movies have taught us anything, it’s that the defensive resources are only effective if they aren’t sabotaged by the internal squabbles of humans. (If you’re not familiar with Romero’s movies, think of what Newman from Seinfeld did in “Jurassic Park”). Thus you’d have to add another parameter, which is the probability in any given period that some jackass sabotages the defensive perimeter, steals the battle bus, etc. If such sabotage eliminates or even appreciably reduces the “safe area” efficacy then human survival in the “safe areas” is contingent on the act of sabotage not occurring. If we assume that p(sabotage) is 1% in any given month, then the probability of sabotage occurring at least once over the course of two years is 1-.99^24, which works out to 21%. That’s not bad, but if we assume a p(sabotage) per month of at least 2.9% then there’s a better than even chance that we’re fucked. Having a dim view of human nature, I don’t like those odds.

So a more elaborated model would not only have to add in parameters for spatial heterogeneity, but also human sabotage. The two probably interact in that the higher the probability of sabotage, the more important it is to have many small resource islands rather than one big resource island. This may have policy implications in terms of how and where we stockpile resources in preparation for the inevitable zombie apocalypse.

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