In recent years the term behavioral economics has arisen in consequence of the growing effort of a significant set of economists to import psychological methods and findings into economics. This body of work issues strong challenges to the use economists have made of rationality in economics....

This paper reviews and puts into perspective recent work reassessing the first and second Fundamental Theorems of Welfare Economics. It assesses the implications of the Greenwald-Stiglitz theorem establishing the (constrained) Pareto inefficiency of market economies with imperfect information...