什麼是Coase Theorem?

Coase Theorem - If the property rights are well defined and transaction costs are zero, then the problems of externalities will be disappeared through bargaining and resources would be efficiently allocated within the society. Transaction costs means the all the time, efforts and money involved to reach a agreement or sign an contract. For example: if there is a factory on upstream of a river that causing thermal and water pollution to the fishing area downstream. The production of fished would be badly affected. However, they can bargian to reach a private contract that the owner of factory can pay some compensation to the owners of the fishes downstream if the property rights are well defined and the cost, time and effort involved could be well covered during the process of bargaining, then the problem of externality i.e. thermal pollution could be resolved and no need for government intervention. In reality, this is seldomly seen without government intervention such as setting up of relevant legislations to prevent thermal and water pollution or taxing the factory owners on the use of water because the transaction costs involved are too great: how much should pay the fishes owner? how to calculate? how long the contract should be lasted? how should pay the consultation fees to reach a opitmal compensation?.... etc, so government intervention is necessary.