Abstract:

Hardin and Zhang′s arguments about the tragedy of the commons are based on the hypothesis that the number of the participants entering into the commons is fixed.But actually it may be variable in the long run because some resources are always public resources even in a long time.And more people will participate in exploiting these resources if there are extra profits，and vice versa.By building mathematic models，we discussed the different results under the following two different institutions，i.e.individual rationality (IR) and collective rationality (CR)，in the long run about the exploitation of this kind of public resources without entrance barriers in this paper.The conclusions are that CR will lead to production inefficiency and less welfare while slowing down the exploiting speed and that IR will get an opposite result.This paper further argues that institutional measures can only be used as a makeshift in dealing with the problem of resource shortage and that the ultimate solution is technical measures.

Key words: the tragedy of the commons, public resources, individual rationality, collective rationality