The welfare weights implicit in any Pareto optimal agreement also serve to identify the
conditions under which the nonperformance of obligations is efficient. When the political
burden of performance to an promisor exceeds the political detriment of nonperformance to the
promisee(s), evaluated at the proper weight or shadow price, nonperformance is jointly
desirable. Roughly speaking, the political costs of performance may be said to exceed the
benefits of performance, just as benefits may exceed costs in the case of a private contract
where both are measured in money. It is in the interests of parties to trade agreements to
facilitate nonperformance under these conditions.