Explanation: Table of Election Method Properties and Criteria
by Michael Ossipoff
December 24, 2012
The table compares voting systems by some precisely-defined criteria, but also by some loosely-defined criteria. The precisely-defined ones have already been defined in previous articles in this Properties article series. I’ll briefly summarize their definitions here. I’ll also explain what I mean by the loosely-defined criteria. The definitions below are brief summaries, not precise definitions.
Some method-name abbreviations
SICT: Symmetrical ICT
Criteria defined in previous articles:
FBC: Favorite-Betrayal Criterion. There should never be any strategic need, incentive or reason to vote someone over your favorite.
CD: Chicken-Dilemma Criterion. The method avoids the chicken dilemma.
LNHe: Later No Help. You needn’t vote for additional candidates to help candidates you’re already voting for.
ZLNHe: 0-info LNHe. In a 0-info election, voting for one or more of a set of candidates shouldn’t decrease the probability that one of them will win.
S. ZLNHe: Strong ZLNHe. As above, but, in a 0-info election, voting for one or more of a set of candidates should increase the probability that one of them will win. The justification of this criterion was explained in a previous article. It’s ZLNHe, but more so.
MMC: Mutual Majority Criterion. A sincere voting majority who prefer a set of candidates to the others should elect one of that set.
Usu. MMC: Usually passes MMC. For pairwise-count methods, that means that it passes MMC unless there is a cycle among the majority-preferred candidates.
CC: Condorcet Criterion. If there are one or more unbeaten candidates, then one of them should win. In a previous article, I included a general CC definition.
LNHa: Later No Harm. Voting for additional candidates, not over already-voted-for candidates, and below the already voted-for candidates if the balloting allows it, should never prevent an already-voted-for candidate from winning.
Participation: Adding a new ballot that votes X over Y shouldn’t change the winner from X to Y.
Consistency: If voting region is divided into parts 1 and 2, and if counting the ballots in part 1 would elect Smith, and counting the ballots in part 2 would elect Smith, then counting all the ballots together shouldn’t elect Jones instead of Smith.
M.A.U.T.: Mono-Add-Unique-Top. Adding a new ballot that votes X over everyone else shouldn’t make X lose.
M.A.T.: Mono-Add-Top. Adding a new ballot that votes X at top shouldn’t make X lose. (M.A.U.T and M.A.T. are more-easily-passed versions of Participation. Because they’re easier to pass, they’re worse to fail.)
Mono R.: Mono Raise. Raising a candidate in your ballot shouldn’t make him/her lose.
IIAC: Independence from Irrelevant Alternatives Criterion. Removing a losing candidate from the ballots and from the election, and then recounting the ballots, shouldn’t change the winner.
Smith: Smith Criterion. If there’s a set of candidate each of whom pairwise-beat everyone outside that set, then the winner should come from that set.
CL: Condorcet Loser. Never elect a candidate who is pairwise-beaten by all of the other candidates. Note: Failing CL sounds bad, but, for a non-complying method to fail CL, the winner would have to be a peculiarly popular Condorcet loser. Additionally, of course would happen only very rarely, if ever.
Clone-Ind.: Clone Independence. Adding a candidate identical to existing ones shouldn’t change the matter of whether the winner is one of those identical candidates. This criterion is more fully-defined in a previous article.
Definitions of loosely-defined criteria
Easy: Loosely-defined, the count should be as easy, having as little count-labor, as that of Approval, or at least Score. Plurality, Approval, Score, and Majority-Judgment all pass.
Enactable: Possessing an unarbitrary, natural, obvious, and simple definition. Doesn’t fail any criteria that Plurality doesn’t fail, and thus is in no way worse than Plurality, and is only a clear improvement over Plurality. As intrinsically easy to enact as Approval or Score would be. Plurality, Approval, and Score pass.
Non-Cplx: The count isn’t as complex as a Condorcet count. The count doesn’t entail a kind of counting significantly different from, or more difficult or complicated than, that of Plurality—even if there is more counting to do, as in the case of IRV. Plurality, Approval, Score, Majority-Judgment, and IRV pass.
Kn u/a: Known u/a strategy. The traditional unimproved Condorcet methods, represented here by Beatpath, are distinguished by generally unknown u/a strategy.
Soc Opt: Social Optimization. Approval and Score uniquely possess social optimizations.
Comments on the Table
FBC-compliance is essential with our current electorate. Most voters have been convinced by the media to believe 1) That the corrupt Democrat is acceptable; and 2) That the winner will always be a Democrat or a Republican; and 3) That the election of the Republican would be an unprecedented and terrible disaster (though it’s been happening periodically).
People who prefer the Democrat to the Republican typically regard the Republican as unacceptable. To anyone who believes the above-specified beliefs, when the method in use is Plurality, IRV, Beatpath, or other FBC-failing method, the optimal strategy requires voting the Democrat over everyone else—which often amounts to burying one’s favorite.
Favorite-burial makes nonsense of the election-result, with obvious adverse societal consequences. Though Beatpath meets CC, CL, Smith, and MMC, its failure of FBC and CD would tend to strategically distort voters’ preferences so much as to eliminate the benefit of meeting CC, CL, Smith and MMC. Because of the need for FBC, and the importance of Easy and Enactable, the only voting system proposals that can be recommended for our current electorate are Approval and Score.
I emphasize that Approval and Score are the only alternative methods proposed that don’t fail criteria met by Plurality. They’re the only methods that can’t be claimed to, in some way, be worse than Plurality. IRV, due to its FBC-failure, is entirely unacceptable and unsuitable for our current electorate. IRV can’t be recommended for our current electorate. But the Greens (GPUS) propose IRV as the single-winner voting system, for the government proposed in their platform.
Of course, for the Greens’ platform to take effect, the Greens would have to be elected to the presidency and most of Congress. Any electorate who could accomplish that, using Plurality, would be an electorate that is competent enough to make good use of IRV. It would be an electorate that wouldn’t believe the media-promotion regarding what is acceptable and what is winnable. It would be an electorate that wouldn’t be as vulnerable to FBC-failure.
So, as I said, such an electorate could make good use of IRV, and IRV’s FBC-failure wouldn’t be the problem that it would be with our current electorate. So, if the Greens enacted IRV, after being elected to the presidency and most of Congress, IRV would be okay. Of course there’d be opportunity to get a better method, such as Approval or Score, via improved powers of initiative or referendum.
I emphasize that, even though, with that electorate, FBC isn’t as necessary it would still remain very desirable. Approval or Score would still be considerably better than IRV, even with that better electorate.
Why bring this up? I don’t want to discourage people working for good voting-system reform. But few if any people seem to be doing that work. I guess that even local voting system initiatives are difficult and expensive. And state initiatives are probably prohibitively expensive and difficult. And genuine improvement depends on widespread improvement at least at the state level.
I encourage and support anyone who is, or intends to be, working to enact Approval or Score, but it’s likely that the only way that voting-system reform will happen will be by electing to office a party that wants to do voting-system reform. And it’s much easier to vote for such a party in the elections that we already have, than to somehow organize and finance a state ballot initiative for voting-system reform. Of course, with the election of such a party, voting-system reform would be one part of a larger package of reforms and improvements.
Thank you for your continued interest in voting systems. Please take a look at some of my other articles on Democracy Chronicles.