ABSTRACT
Why should countries contribute voluntarily to the solution of international and global problems? Often such problems are an international public bad, and participation in a common approach to solve or mitigate the problem is like voluntarily contributing to the production of an international public good. A prominent example is climate change. No country can be excluded from enjoying the benefits once the public good has been delivered. Economically speaking, it looks wiser to leave the provision to other countries and reap the benefits of the good without any effort or sacrifice. Every economist knows the refutation of this rhetorical question. When all agents reason like this, the public good will not be provided at all, or at a level far too low relative to the optimum level of provision.
