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As far as I can tell the Schulze method does not satisfy the independence of irrelevant alternatives condition, and so adding an extra option can have an effect
by contravariant 5y ago
As far as I can tell the Schulze method does not satisfy the independence of irrelevant alternatives condition, and so adding an extra option can have an effect on the end result. However the upside is that you can actually recalculate what the result would have been if you remove one of the options, since the voting results are summarized as the number of people who prefer A to B, which shouldn't change if you remove one of the options.
- nulbyte 5y agoIf you remove option A, it would necessarily be a different outcome for someone who would have voted for A over B.
- YetAnotherNick 5y agoI think what GP meant that if you have two identical option A and B, we could remove A after voting and it would have the same result as not having option in the first place.
- sjmm1989 5y agoI think you got their intent in sharing their belief correct; but their belief is wrong. If you remove A as a choice, or B, people might go with their next preferred option instead of just not voting at all, etc. This means you can't know for sure that results would equal the same with or without that option, because you cannot actually assume all actors will vote the same every time. To even begin to think such a thing as true is just asinine when the world proves to us on a daily basis that people are willing to compromise on their beliefs all the time. (No offense.)
- winkeltripel 5y agoBut its a ranked ballot. The sort should be stable.
- sjmm1989 5y agoThe problem with this is that it is thinking in absolutes during a situation where people are often very willing to compromise their own beliefs just to be able to provide an answer. In normal elections we see this with people who don't like any choice, but don't want to spoil their ballot. So they pick their next best favorite. This means that if A is removed, people might pick B or C instead just because A isn't there. People are tricky. Hard to pin down what's exactly going to happen every time. There are distinguishable patterns and such; but ultimately you can't rely on them as if they are infallible.
- contravariant 5y agoAs long as you assume people aren't suddenly going to prefer A to B when C is there and prefer B to A when C isn't then you can safely recalculate the result. Of course people might not necessarily act rationally but you've got to draw a line somewhere, otherwise elections are simply undefined behaviour and talking about properties of elections becomes meaningless.
- couchand 5y agoThe behavior you describe isn't at all irrational: in a nutshell that's the effect that propelled Biden to the White House.
- winkeltripel 5y agoI don't understand your point. In ranking presidential candidates, most left-or-center-leaning voters would rank any and every Democrat above any and every Republican, with Trump as their very last choice. So the presence or not of any specific candidate doesn't change the outcome. They would have voted in whomever the Democrat Nominee was.
- couchand 5y agoThere was lots of reporting in 2020 about Democratic voters who preferred another candidate throwing their support behind Biden based on the idea that he was best positioned to win in the general election.