Retour
  • lundi 15 nov.

[Séminaire CREM] Monotonicity Violations under Plurality with a RunOff : The Case of French Presidential Elections.

Présentation de Halil Berkay TOSUNLU, Paris Dauphine PSL, LAMSADE

MRSH SH027 / Zoom

[Séminaire CREM] Monotonicity Violations under Plurality with a RunOff :  The Case of French Presidential Elections.

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.

UFR SEGGAT - MRSH

Université de Caen Normandie

  • Novembre 2021

    • Lundi 15 14:15 - 15:45