Monotonicity violations under plurality with a runoff: the case of French presidential elections

Umut Keskin, Remzi Sanver and H. Berkay Tosunlu
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Umut Keskin: Istanbul Bilgi University
H. Berkay Tosunlu: LAMSADE - Laboratoire d'analyse et modélisation de systèmes pour l'aide à la décision - Université Paris Dauphine-PSL - PSL - Université Paris Sciences et Lettres - CNRS - Centre National de la Recherche Scientifique

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Abstract: A voting rule is monotonic if a winning candidate never becomes a loser by being raised in voters' rankings of candidates, ceteris paribus. Plurality with a runoff is known to fail monotonicity. To see how widespread this failure is, we focus on French presidential elections since 1965. We identify mathematical conditions that allow a logically conceivable scenario of vote shifts between candidates that may lead to a monotonicity violation. We show that eight among the ten elections held since 1965 (those in 1965 and 1974 being the exceptions) exhibit this theoretical vulnerability. To be sure, the conceived scenario of vote shifts that enables a monotonicity violation may not be plausible under the political context of the considered election. Thus, we analyze the political landscape of these eight elections and argue that for two of them (2002 and 2007 elections), the monotonicity violation scenario was plausible within the conjuncture of the time.

Keywords: French presidential elections; plurality with a runoff; monotonicity (search for similar items in EconPapers)
Date: 2022
New Economics Papers: this item is included in nep-cdm and nep-pol
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Published in Social Choice and Welfare, 2022, 59 (2), pp.305-333. ⟨10.1007/s00355-022-01397-4⟩

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Journal Article: Monotonicity violations under plurality with a runoff: the case of French presidential elections (2022)
Working Paper: MONOTONICITY VIOLATIONS UNDER PLURALITY WITH A RUNOFF: THE CASE OF FRENCH PRESIDENTIAL ELECTIONS (2021)
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Persistent link: https://EconPapers.repec.org/RePEc:hal:journl:hal-03767264

DOI: 10.1007/s00355-022-01397-4

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