Contributions to International Public Goods and the Notion of Country Size

There is no consistent notion of country size in the literature on the voluntary provision of an international public good. This paper suggests preference-adjusted GNP as a useful index of size. Defining a country's size in that manner, contributing countries are unambiguously larger than free riders. But, interestingly, a larger contributing country does not necessarily contribute more than a smaller one. In the special case when all the contributing countries are of equal size, the one with stronger (weaker) preference for the public good will contribute less (more). In another special case when one of the countries is sufficiently larger than the rest, only this largest country will contribute. These results may help in explaining the diversity in cost-sharing across different international public goods.