Schulze STV

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Schulze STV is a PR method that reduces to Schulze in the single-winner case. It was designed by Markus Schulze to maximally resist Hylland free riding while still being proportional for Droop solid coalitions.

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Schulze STV can be used to find a Smith set of winner sets, which any cycle resolution method other than Schulze can be applied to find the winner. This Smith set can be found by looking for the smallest group of winner sets such that each winner set in the group pairwise beats all winner sets not in the group. One might also use the concept of the beat-or-tie path to find the Smith set.

Some ideas for adapting non-Schulze cycle resolution methods to the Smith set:

  • Condorcet-IRV hybrids: each voter's 1st choices are considered to be the winner set(s) that have the most of their most-preferred candidates in them, their 2nd choices are the winner set(s) with the second-most of their most-preferred candidates, etc.
  • Condorcet-cardinal hybrid methods: One can either use a cardinal PR method with constraints applied in order to guaranteeably result in a Smith winner set, or can use a cardinal method to pick the Smith winner set that is overall most satisfying. See Algorithmic Asset Voting#The multi-winner Smith Set and Smith-efficient cycle resolution.

Schulze STV always picks a winner set from the Smith set, according to Schulze's own multi-winner generalization of the Smith criterion.