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Monotonicity Anomalies in Scottish Local Government Elections

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  • David McCune
  • Adam Graham-Squire

Abstract

Single Transferable Vote (STV) is a voting method used to elect multiple candidates in ranked-choice elections. One weakness of STV is that it fails multiple fairness criteria related to monotonicity and no show paradoxes. We analyze 1,079 local government STV elections in Scotland to estimate the frequency of such monotonicity anomalies in real-world elections, and compare our results with prior empirical and theoretical research about the rates at which such anomalies occur. In 62 of the 1079 elections we found some kind of monotonicity anomaly. We generally find that the rates of anomalies are similar to prior empirical research and much lower than what most theoretical research has found. The STV anomalies we find are the first of their kind to be documented in real-world multiwinner elections.

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  • David McCune & Adam Graham-Squire, 2023. "Monotonicity Anomalies in Scottish Local Government Elections," Papers 2305.17741, arXiv.org, revised Oct 2023.
    • Handle: RePEc:arx:papers:2305.17741
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    Cited by:

    1. David McCune, 2024. "Single Transferable Vote and Paradoxes of Negative and Positive Involvement," Papers 2406.20045, arXiv.org, revised Nov 2024.

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