Monday, March 23, 2009

Fisheries provide insight into how to stabilize the economy

A few days ago I was reading through my backlog of dead-tree Scientific Americans and I came across an interesting article tucked in the back. It's essentially a summary of a study conducted by George Sugihara, a mathematician and theoretical ecologist at the Scripps Institution of Oceanography. The study supports the idea that the best way to manage fisheries is not to throw back the small fish, as is currently done, but throw back the big ones. I have believed this same theory for a long time, because we don't want to put an evolutionary pressure on the system to produce smaller individuals, but the article provides evidence that the effects are more immediate and extreme than evolutionary processes alone would produce:

Imagine, Sugihara says, a 500-pound fish in an aquarium. Feed it more, and it gets fatter. Feed it less, and it gets thinner. The population (of one) is stable. But put 1,000 half-pound fish in that aquarium, and food shortages could result in the deaths of hundreds, because the small fry have less stored body fat—and therefore cannot ride out a short famine. Food abundance does not necessarily mean all the fish get bigger, either; it could en­courage reproduction and a population boom—which might in turn overwhelm the food supply and lead to another bust. It is an unstable system. “That’s the reality of fisheries, of economies, of a lot of natural systems,” Sugihara says.

Another researcher actually reproduced this effect in fish tanks. Over five generations, David Conover of Stony Brook University harvested large fish from his tanks, and then discovered that the population had a smaller average size. That should come as no surprise.

This idea is very obviously applicable to economics, which is widely regarded as a chaotic system (though to be fair, there is still some debate on that point), and the article makes mention of that many times, even noting that the chaotic systems of fisheries are so like financial networks that Deutsche Bank hired Sugihara for a time. The article does not expand on this connection as much as I would have liked, but even so, this study can be seen as evidence in favor of the idea that penalizing the big players for their success leads to both a less stable economy and a smaller average size. It's open to debate as to what the correct analogy with the economy is (fish as individuals or corporations, for example), but the specific analogy doesn't matter when we're talking about the broad trends of this class of mathematical system. I don't think anyone thinks those two outcomes are desirable, regardless of their ideology. I'd hesitate to say that it's actually evidence in support of trickle-down economic theories without some more direct information, but it is very plainly evidence against punishing the successful and rewarding the unsuccessful. That shouldn't come as any surprise either.

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