Coasean theorem

In law and economics, the Coase theorem (/ˈkoʊs/) describes the economic efficiency of an economic allocation or outcome in the presence of externalities. The theorem is significant because, if true, the conclusion is that it is possible for private individuals to make choices that can solve the problem of market externalities. The theorem states that if the provision of a good or service results in an externality and trade in that good or service is possible, then bargaining will lead to a Pareto efficient outcome regardless of the initial allocation of property. A key condition for this outcome is that there are sufficiently low transaction costs in the bargaining and exchange process. This 'theorem' is commonly attributed to Nobel Prize laureate Ronald Coase (quotations noting that Coase's theorem is not a theorem in the strict mathematical sense).