A central authority, possessing tax and expenditure responsibilities, can readily provide an efficient level of a public good. Climate change mitigation lacks a central authority. Thus, voluntary arrangements must replace coercive arrangements; significant under-provision must be expected. Potential contributors have strong incentives to free ride or ride cheaply. The players - the many nations of the world - are quite disparate. They thus frame negotiations from their own standpoints, making stalemate likely. Moreover, the focal-point solution where contributions are proportional to benefits clashes with the disproportionate cheap-riding incentives of little players. Our proposed solution, the Cheap-Riding Efficient Equilibrium (CREE), defines the relative contributions of players of differing size (or preference intensity) to reflect cheap riding incentives, yet still achieves Pareto optimality. CREE establishes the Alliance/Nash Equilibrium as a base point. From that point it proceeds to the Pareto frontier by applying the principles of the Lindahl Equilibrium (a focal point) or the Nash Bargaining Solution (a standard approach). We test the Alliance Equilibrium model using nations' Intended Nationally Determined Contributions at the Paris Climate Change Conference. As hypothesized, larger nations made much larger pledges in proportion to their Gross National Incomes. We apply our theory to examine the Nordhaus Climate Club proposal.
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