Figure 1.

Multi-patch SIR model. (a) Global, fully cooperative optimum (green line) and the independent, non-cooperative optimum (Nash equilibrium), given in red for increasing numbers of identical interconnected countries. Parameters: R₀ = 5, coupling strength = 10μ/(n − 1), a_i = 0.1, c_Ii = 5. Costs (b) and realized coverage (c) for a system of 15 identical interconnected countries, for increasing coalition size (x-axis). Green and red lines show global and independent optima (as in (a)), black lines show the optimum realized by the countries in the coalition, grey lines show optimum for countries that have not joined the coalition. Other parameters as in (a).