0-info Later-No-Help: Difference between revisions
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(abbreviated ZLNHe. LNHe stands for [[Later-No-Help]])
▲== Definition of ZLNHe: ==
'''Supporting definitions:'''
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'''Zero-Info LNHe (ZLNHe):'''
{{definition|In a 0-info election, voting above bottom one or more of some certain set of candidates shouldn't decrease the probability that the winner will come from that set, as compared to voting them all at bottom.}}
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word "weakening" hardly even applies. I suggest that, with a voting system complying with ZLNHe or Strong ZLNHe, there's no need to vote for unacceptable candidates. (just as can be said for methods complying with the slightly stronger LNHe).
{{definition|Same as ZLNHe, except that voting one or more members of that set over bottom should ''increase'' the probability that the winner will come from that set (instead of just not decreasing that probability).}}
▲== Definition of Strong ZLNHe: ==
Someone could argue that a compliance with Strong 0-info Probabilistic Later-No-Help could, and should more properly, be called a failure of a 0-info probabilistic Later-No-Harm.
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Things are different when we're talking about probabilities in a 0-info election.
When, in that 0-info election, the probability of electing an unacceptable isn't reduced by ranking
I name Strong ZLNHe in terms of LNHe because the relevant thing about it is the absence of need to rank unacceptable candidates. Strong ZLNHe simply achieves what ZLNHe achieves, but more so.
If there were a little not-so-reliable information about the relative winnabilities of unacceptables X and Y, then there could begin to be some incentive to rank one over the other. Compliance with Strong ZLNHe instead of just ZLNHe would more strongly outweigh that incentive to rank
So, instead of a failure of a 0-info probabilistic Later-No-Harm, a compliance with Strong ZLNHe is more relevantly regarded as a compliance with a stronger and more reassuring 0-info probabilistic Later-No-Help.
Of course, all methods that meet LNHe also meet ZLNHe.▼
▲== Complyng methods: ==
▲Of course all methods that meet LNHe also meet ZLNHe.
Methods that comply with LNHe include [[Approval voting]], Score Voting (also called [[Range voting]]), and IRV.
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Ordinary ICT, and traditional Condorcet methods don't comply with LNHe, ZLNHe or Strong ZLNHe.
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▲== Definition of Later-No-Help (LNHe): ==
When, while making out your ballot, you've voted for some candidates, then you don't need to vote for additional candidates in order to fully help the candidates you've already voted for.
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To fully help a candidate is to vote in a way that does as much as possible toward making him/her win.
}}
▲[end of LNHe definition]
▲== Commentary: ==
LNHe is relevant to bottom-end strategy. For example, many rank methods that fail LNHe have bottom-end strategy that calls for ranking unacceptable candidates in reverse order of winnability. A method that meets LNHe doesn't have such a strategy-need. LNHe-complying methods don't need bottom-end strategy.
Some methods that don't strictly meet LNHe can meet ZLNHe and maybe Strong ZLNHe. For example,
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▲== A Few Compliance Demonstratons: ==
(This will make more sense after reading the definition of [[Symmetrical ICT]] (SITC) )
In [[Symmetrical ICT]], bottom-voting X and Y (typically done by not ranking them)
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Whichever one could be made to beat the other, your bottom-voting of X
and Y counts toward that pairwise beaten-ness. In the event that
SICT's beat-condition rule says that both X and Y beat
SICT says that the one that beats the other is the one ranked over the
other on more ballots than vice-versa.
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number of X>Y ballots be greater than the number of Y>X ballots you're
voting for X being the one that beats the other, in the event of both
beating
So, if you knew that, then it would be better to rank X and not Y. But
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that the winner will come from {X,Y}.
In a large official public election, pairwise ties are vanishingly
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[end of compliance and noncompliance demonstrations]
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You might say, "How is Strong ZLNHe compliance better than ordinary ZLNHe compliance?" Well,▼
▲You might say, How is Strong ZLNHe compliance better than ordinary ZLNHe compliance? Well,
▲suppose that there were a little not-too-reliable information
suggesting something about likely beaten-ness of X and Y by other candidates.
That could tend to make some strategic incentive to
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[[Symmetrical ICT]] is the only method that I know of that meets Strong ZLNHe without meeting LNHe.
[[Category:Voting system criteria]]
{{fromelectorama|0-info LNHe}}
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