Miscellany: Tragedy of the Commons, writ small

"The Tragedy of the Commons" is a name for a very old concept - the problem that emerges when individuals (who are assumed to be selfish by nature) set upon a finite resource.

From Garret Hardin's essay:
============


The tragedy of the commons develops in this way. Picture a pasture open to all. It is to be expected that each herdsman will try to keep as many cattle as possible on the commons. Such an arrangement may work reasonably satisfactorily for centuries because tribal wars, poaching, and disease keep the numbers of both man and beast well below the carrying capacity of the land. Finally, however, comes the day of reckoning, that is, the day when the long-desired goal of social stability becomes a reality. At this point, the inherent logic of the commons remorselessly generates tragedy.

As a rational being, each herdsman seeks to maximize his gain. Explicitly or implicitly, more or less consciously, he asks, "What is the utility to me of adding one more animal to my herd?" This utility has one negative and one positive component.

1) The positive component is a function of the increment of one animal. Since the herdsman receives all the proceeds from the sale of the additional animal, the positive utility is nearly +1.
2) The negative component is a function of the additional overgrazing created by one more animal. Since, however, the effects of overgrazing are shared by all the herdsmen, the negative utility for any particular decision-making herdsman is only a fraction of 1.

Adding together the component partial utilities, the rational herdsman concludes that the only sensible course for him to pursue is to add another animal to his herd. And another; and another. . . . But this is the conclusion reached by each and every rational herdsman sharing a commons. Therein is the tragedy. Each man is locked into a system that compels him to increase his herd without limit--in a world that is limited. Ruin is the destination toward which all men rush, each pursuing his own best interest in a society that believes in the freedom of the commons. Freedom in a commons brings ruin to all.

===============

There's some controversy over whether this is actually what happens in real life. Shouldn't it be obvious to everyone involved that adding animals indefinitely isn't possible?

Anyhoo, I only point out the metaphor to relate the tale of "Scion Girl." We have parking spaces located all around our condos, and they're more or less a free-for-all in terms of who gets to park where. Most people park next to their apartments, so disagreements are rare. Unfortunately, the girl from the next building over constantly steals our parking spot, and she drives a white Scion tC. I'm even thinking of putting a sign on her car demanding she doesn't park there.