TRAGEDY OF THE COMMONS
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 satisfactorily for because tribal wars, 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 and logic of the commons remorselessly generates tragedy. As a rational being, each herdsman seeks to maximize his gain. What is the utility to me of adding one more animal to my herd?" Since the herdsman receives all the proceeds from the sale of the additional animal, the positive utility is nearly 1. The negative impact is the additional overgrazing created by one more animal. However, the effects of overgrazing are shared by all the herdsmen; the negative utility for any particular herdsman is only a fraction of -1. The only sensible course for him to pursue is to add another animal to his herd, and another, and so forth. But this is the conclusion reached by each and every rational herdsman sharing a commons. Therein lies the tragedy.