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Public Choice

, Volume 161, Issue 1–2, pp 1–9 | Cite as

Frequency of monotonicity failure under Instant Runoff Voting: estimates based on a spatial model of elections

  • Joseph T. Ornstein
  • Robert Z. Norman
Article

Abstract

It has long been recognized that Instant Runoff Voting (IRV) suffers from a defect known as nonmonotonicity, wherein increasing support for a candidate among a subset of voters may adversely affect that candidate’s election outcome. The expected frequency of this type of behavior, however, remains an open and important question, and limited access to detailed election data makes it difficult to resolve empirically. In this paper, we develop a spatial model of voting behavior to approach the question theoretically. We conclude that monotonicity failures in three-candidate IRV elections may be much more prevalent than widely presumed (results suggest a lower bound estimate of 15 % for competitive elections). In light of these results, those seeking to implement a fairer multi-candidate election system should be wary of adopting IRV.

Keywords

Voting theory Instant Runoff Voting Agent-based modeling Monotonicity 

JEL Classification

D72 

Notes

Acknowledgements

The authors thank Ross A. Hammond and the anonymous reviewers for insightful comments and suggestions. Any errors remain the responsibility of the authors.

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Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  1. 1.Department of Political ScienceUniversity of MichiganAnn ArborUSA
  2. 2.Department of MathematicsDartmouth CollegeHanoverUSA

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