Contingent commodities and implementation

In this note we study the relevance of using contingent commodity allocatio ns when states are not directly contractible. In such a setting, a continge nt commodity allocation takes the form of a social choice function, and the question is whether this function is implementable. Using only very mild a ssumptions on the rule for selecting contingent commodity allocations, we d erive a strong negative result which proves to be robust with respect to di fferent solution concepts employed for implementation. These findings have interesting implications for the interpretation of Arrow-Debreu economies. (C) 2000 Elsevier Science S.A. All rights reserved. JEL classification: D50 .