On the performance of the Shapley Shubik and Banzhaf power indices for the allocations of mandates

Fabrice Barthélémy (), Mathieu MARTIN () and Vincent R. Merlin ()
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Mathieu MARTIN: THEMA, Université de Cergy-Pontoise

No 2007-25, THEMA Working Papers from THEMA (THéorie Economique, Modélisation et Applications), Université de Cergy-Pontoise

Abstract: A classical problem in the power index literature is to design a voting mechanism such as the distribution of power of the different players is equal (or closer) to a pre established target. This tradition is especially popular when considering two tiers voting mechanisms: each player votes in his own jurisdiction to designate a delegate for the upper tier; and the question is to assign a certain number of mandates for each delegate according the population of the jurisdiction he or she represents. Unfortunately, there exist several measures of power, which in turn imply different distributions of the mandates for the same pre established target. The purposes of this paper are twofold: first, we calculate the probability that the two most important power indices, the Banzhaf index and the Shapley-Shubik index, lead to the same voting rule when the target is the same. Secondly, we determine which index on average comes closer to the pre established target.

Keywords: Banzhaf; Shapley-Shubik; power indices (search for similar items in EconPapers)
JEL-codes: C7 D7 (search for similar items in EconPapers)
New Economics Papers: this item is included in nep-cdm, nep-gth and nep-pol
Date: Written 2007
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