Les Cahiers de Recherche - HEC Paris
Unanimity and the aggregation of multiple prior opinions
Abstract: Author's abstract. In a situation of decision under
uncertainty, a decision maker wishes to choose according to the maxmin
expected utility rule, and he can observe the preferences of a set of
experts who all share his utility function and all use the maxmin EU rule.
This paper considers rules for aggregating the experts’ sets of priors into
a set that the decision maker can use.
It is shown that, in a multi
profile setting, among the rules that allow the decision maker’s evaluation
of an act to depend only on the experts'evaluations of that act, the only
rule satisfying the standard unanimity or Pareto condition on preferences
is the “set of weights” aggregation rule, according to which the decision
maker’s set of priors is the set of weighted averages of the priors in the
experts’ sets, with the weights taken from a set of probability vectors
over the experts. An analogous characterisation is obtained for variational
Keywords: aggregation of beliefs; opinion pooling; ambiguity; multiple priors; pareto condition; variational preferences; (follow links to similar papers)
JEL-Codes: D70; D80; (follow links to similar papers)
26 pages, January 19, 2012
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