This paper argues that sharing rules have served to reduce the inefficiency caused by common pool externalities in many developing societies. To this end, a two-sector model of renewable resource use is employed where sharing rules are interpreted as implicit resource taxes. The model is applied to the island economy of Lofanga in the Kingdom of Tonga. The model generates a growth pattern which is consistent with the observed time paths of population and the resource stock. Cyclical fluctuations are weak even in the absence of resource taxation because the intrinsic growth rate of the resource is high.