Arrow's Theorem (2014)

Re:Arrow's Theorem (2014) by KerrickStaley on Friday November 10, 2017 @08:37PM (#15674510)

RCV has some weaknesses compared to Condorcet methods (which use the same voting mechanism of ranking candidates but different ways of determining the winner). RCV can punish people for voting according to their true preferences.

For example, say a country is 49% Republicans and 51% Democrats. In addition, a Socialist candidate is running. 30% of the Democrats actually prefer the Socialist candidate, but under a plurality system they would vote for the Democrat candidate because the Democrat has broader appeal.

If those 30% chose to rank the Socialist as their #1 choice, then the Republican will win the election, because the Democrat will be eliminated in the first round. So the Democrats are incentivized to not vote their actual preference.

Look at the various Condorcet methods [1], and also check out Approval Voting [2] for a system that produces fairer outcomes without the complexity of RCV/Condorcet.

[1] https://en.wikipedia.org/wiki/Condorcet_method

[2] https://en.wikipedia.org/wiki/Approval_voting

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Re:Arrow's Theorem (2014) by bradbeattie on Friday November 10, 2017 @09:54PM (#15674747)

I'm with you on Condorcet methods producing more equitable results between tactical and non-tactical voters, and I'd love it to be used for the election of singular positions (e.g. a mayor, a president, etc). But all single winner systems distort outcomes in parlimentary bodies (house of representatives, Canada's parliament, etc). Look instead to MMP or STV.

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