Sunday, April 10, 2005

The Tragedy of the Commons

The Tragedy of the Commons is an economics term. The story goes that, in medieval England, ever town had a pasture that could be used by all the villagers. A typical village, for example, had enough pasture to support 100 cows. The concept is that one villager would decide to put two cows on the common pasture and double his income. The other villagers would see this and put all of their cows in the pasture. The trouble is, the pasture could only support 100 cows, and so it would soon become a mud patch full of scrawny cows.

Here's the trouble with this scenario. The peasants are not stupid. A few would notice that the milk was drying up, and decide to have steaks rather than milk. The peasants would cut their loses, either by moving their cows back to their own pasture, or by eating a few. Either way, the cow population would be brought back into balance with the available pasture. The only time that this would not be the case is if additional exploitation caused irreparable harm, yet such instances are few.

6 Comments:

Blogger Hamlette said...

Oh, I thought the Tragedy of the Commons was when they decided to split up those commons and put fences on them (kinda like killing the open range in the American West). There's a lot about that sort of thing in one or two of the Jack Aubrey/Stephen Maturin books...

9:15 AM  
Blogger Noumenon said...

The things you're talking about the peasants doing are the results of the tragedy of the commons. They could have raised another cow on their own land for steak, and kept the one on the commons for milk. But now they're impoverished and get to have only one cow and pay for its fodder, instead of two cows with one eating for free.

11:09 AM  
Blogger Octavo Dia said...

Yes, but the point is the the tragedy of the commons is self-correcting.

11:41 PM  
Blogger Octavo Dia said...

What you're talking about, hamlette, was called "enclosure" and happened during the First Industrial Revolution, when all of the common pasture was fenced off for sheep walks.

11:42 PM  
Blogger Hamlette said...

Yup, enclosure, that's what I'm talking about. Very sad, that enclosure business. No more lovely grassy area to wander about and hunt rabbits in. Hooray for Admiral Aubrey for quashing the enclosure efforst in his district!

10:45 PM  
Blogger Noumenon said...

If the peasants left their 200 cows on the pasture and went away, and then 150 died of famine because they ate all the grass too short, the situation would still be "self-correcting," in the sense that "the cow population would be brought back into balance with the available pasture." The problem is instead of an equilibrium of 100 fat cows on the pasture you have 50. Or instead of 60 million bison on the plains you have six hundred. Sure you can take the ones you have left and send them out to breed but the bison-eating industry is not going to recover from what you did to the commons.

I think your dispute rests heavily on "this would not be the case is if additional exploitation caused irreparable harm, yet such instances are few." It doesn't take irreparable harm. There's a tragedy of the commons effect when everybody decides to drive on the free highways at the same time. The traffic jam clears up in an hour but you never get that time back. And people drive less the next couple days but eventually they come back again, drawn tragically and irresistibly to their share of the commons.

1:18 AM  

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