A Complete Analysis of Full Pareto Efficiency in Financial Markets for Arbitrary Preferences



This paper provides a complete analysis of the necessary and sufficient conditions for financial markets to achieve fully Pareto-efficient allocation of aggregate wealth through trade in economies with arbitrary preferences. We show that full Pareto efficiency obtains only if the market structure of contingent claims spans the information partition of a minimal aggregate wealth statistic and a Halmos-Savage sufficient statistic for the beliefs of the traders. All the known allocation efficiency results in the literature due to Arrow, Hakansson, John, Ross, and others are unified by this result.