ON THE NONEXISTENCE OF BLACKWELLS THEOREM-TYPE RESULTS WITH GENERAL PREFERENCE RELATIONS

A well-known theorem of Blackwell states that, when quantity of inform ation is properly defined, every expected utility decision maker prefe rs more information to less; for more general preferences, however, th e theorem is no longer true. In this article, we investigate the exten t to which Blackwell's Theorem does not hold and describe conditions, and situations, under which information is still valuable. We also sho w that, for many types of additions of information, there exists a dec ision maker who will reject this information.