Distributed Multi-Voting: Difference between revisions
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Aldo Tragni (talk | contribs) (Add DMV procedure (criteria are missing)) |
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# For each single vote, get the normalized votes on all subsets conteining at least 2 candidates. Add up the points for each candidate of the normalized votes, obtaining the converted original vote.
# After obtaining all the converted original votes, the candidate with the lowest sum, of the converted votes, loses.
# Eliminate the loser from all the original votes, and setting the candidate with the lowest score in each vote to 0. Repeat the whole process from the beginning, leaving as many winner as you like.
% of victory: got the winners, eliminate the losers from all the original votes and normalize. The % of victory are obtained from the sum of the points for each candidate.
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If the candidates of the subset, in a certain vote, all have the same score different from 0 then, before normalization, don’t set the lowest score to 0.
==Criteria==
{| class="wikitable" style="text-align:center"
<!-- criteria headers -->
|- style="font-size:80%; border-bottom: 2px solid #a0a0a0;"
! rowspan=1 |
! rowspan=1 style="border-left: 2px solid #a0a0a0;" | [[Majority criterion|Majority]]
! rowspan=1 | [[Majority loser criterion|Maj. loser]]
! rowspan=1 | [[Mutual majority criterion|Mutual maj.]]
! rowspan=1 | [[Condorcet criterion|Condorcet]]
! rowspan=1 | [[Condorcet loser criterion|Cond. loser]]
! rowspan=1 | [[Smith criterion|Smith]]
! rowspan=1 | [[Independence of irrelevant alternatives|IIA]]
! rowspan=1 | [[w:Independence of clones criterion|Clone proof]]
! rowspan=1 style="border-left:2px solid #a0a0a0;" | [[Monotonicity criterion|Monotone]]
! rowspan=1 | [[Consistency criterion|Consistency]]
! rowspan=1 | [[Participation criterion|Participation]]
! rowspan=1 style="border-left:2px solid #a0a0a0;" | [[Later-no-help criterion|Later-no<br>Help]]
! rowspan=1 | [[Later-no-harm criterion|Later-no<br>Harm]]
! rowspan=1 | [[Favorite betrayal criterion|Favorite<br>betrayal]]
|- style="font-size:80%;"
<!-- Methods -->
|-
! [[Distributed_Multi-Voting|DMV]]
! style="background: #ffc7c7; font-weight: inherit;" | No*
! style="background: #ffc7c7; font-weight: inherit;" | No*
! style="background: #ffc7c7; font-weight: inherit;" | No*
! style="background: #ffc7c7; font-weight: inherit;" | No*
! style="background: #ffc7c7; font-weight: inherit;" | No*
! style="background: #ffc7c7; font-weight: inherit;" | No*
! style="background: #ffc7c7; font-weight: inherit;" | No*
! style="background: #ffc7c7; font-weight: inherit;" | No*
! style="background: #ffc7c7; font-weight: inherit;" | No*
! style="background: #ffc7c7; font-weight: inherit;" | No*
! style="background: #ffc7c7; font-weight: inherit;" | No*
! style="background: #ffc7c7; font-weight: inherit;" | No*
! style="background: #ffc7c7; font-weight: inherit;" | No*
! style="background: #ffc7c7; font-weight: inherit;" | No*
|}
{| class="wikitable" style="text-align:center; float: right; margin: 0px 20px 5px 20px;"
|- style="font-size:80%; border-bottom: 2px solid #a0a0a0;"
! rowspan=1 style="border: none; background: white;" |
! A
! B
! C
! D
|-
|- style="font-size:80%; font-weight: inherit; background: white;"
! style="text-align:right;" | [1] original vote
| style="font-weight: bold;" | 100
| 0
| 0
| 0
|-
|- style="font-size:80%; border-bottom: 2px solid #a0a0a0; font-weight: inherit; background: white;"
! style="text-align:right;" | converted vote
| 700
| 0
| 0
| 0
|-
|- style="font-size:80%; font-weight: inherit; background: white;"
! style="text-align:right;" | [2] original vote
| style="font-weight: bold;" | 99
| style="font-weight: bold;" | 1
| 0
| 0
|-
|- style="font-size:80%; border-bottom: 2px solid #a0a0a0; font-weight: inherit; background: white;"
! style="text-align:right;" | converted vote
| 697
| 303
| 0
| 0
|-
|- style="font-size:80%; font-weight: inherit; background: white;"
! style="text-align:right;" | [3] original vote
| style="font-weight: bold;" | 96
| style="font-weight: bold;" | 4
| style="font-weight: bold;" | 1
| 0
|-
|- style="font-size:80%; border-bottom: 2px solid #a0a0a0; font-weight: inherit; background: white;"
! style="text-align:right;" | converted vote
| 686
| 292
| 122
| 0
|-
|- style="font-size:80%; font-weight: inherit; background: white;"
! style="text-align:right;" | [4] original vote
| style="font-weight: bold;" | 51
| style="font-weight: bold;" | 49
| 0
| 0
|-
|- style="font-size:80%; border-bottom: 2px solid #a0a0a0; font-weight: inherit; background: white;"
! style="text-align:right;" | converted vote
| 553
| 447
| 0
| 0
|-
|- style="font-size:80%; font-weight: inherit; background: white;"
! style="text-align:right;" | [5] original vote
| style="font-weight: bold;" | 75
| style="font-weight: bold;" | 20
| style="font-weight: bold;" | 5
| 0
|-
|- style="font-size:80%; border-bottom: 2px solid #a0a0a0; font-weight: inherit; background: white;"
! style="text-align:right;" | converted vote
| 627
| 342
| 131
| 0
|-
|- style="font-size:80%; font-weight: inherit; background: white;"
! style="text-align:right;" | [6] original vote
| style="font-weight: bold;" | 35
| style="font-weight: bold;" | 33
| style="font-weight: bold;" | 32
| 0
|-
|- style="font-size:80%; border-bottom: 2px solid #a0a0a0; font-weight: inherit; background: white;"
! style="text-align:right;" | converted vote
| 490
| 381
| 229
| 0
|-
|}
No* = the DMV can fail all the criteria but the cases in which they fail are extremely rare (less frequent than many others voting systems that don't meet the same criteria).
The original vote of the voter through point 1 of the procedure is converted, and the vote obtained is in part of the type:
* ranking (Borda), because the points tend to be distributed linearly in the converted vote (see all cases).
* range (Score), because by distributing the points in quite different quantities, the candidates tend to keep their score in the converted vote (see A,B,C in cases [1], [2], [3], [5] ).
* cumulative, because the points distributed in the converted votes are however limited and fixed (700 in the case [1], 1000 in the cases [2] and [4], 1100 in the cases [3], [5], [6] based the number of candidates evaluated).
The DMV in any case meets the [[Independence of Worst Alternatives|IWA]].
===Resistance to strategic votes===
The DMV is extremely resistant to tactical votes, that ignore the election results.
The way in which the converted vote is obtained means that the voter doesn’t have a great interest in accumulating their points all on the same candidate. In cases [1] and [2] it’s noted that the addition of 1 point on B, left the score of A practically unchanged in the converted vote, but in case [2] it obtained 303 points for B (same speech observing the case [3] or even [5] ); this means that the voter has an interest in expressing his preference towards B. At the same time, the voter doesn’t even have the interest of giving his limited points to candidates he doesn’t really support (reduced dispersion of points) .
The DMV can be subject to tactical votes in which candidates change the order of their preferences based on the results of the elections; to use these tactical votes you must:
* are sufficiently aware of the expected results of an election (hard).
* fully understand the functioning of the DMV.
* be willing to take risks, because these tactical votes can backfire on the voter if they fail.
Overall in practical contexts it’s very difficult to create an effective strategic vote in the DMV.
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