You’re invited to vote in a poll between 7 voting-systems at the Condorcet Internet Voting Service.

Here’s a link to the poll: 

https://civs.cs.cornell.edu/cgi-bin/vote.pl?id=E_fa18e6840b070f44

It’s a poll to find out:

1. which ones of 7 good voting-systems would be accepted

and

2. which of them is the overall favorite among poll-respondents.

It’s a rank-balloting poll, in which you’ll be asked to rank the voting-systems in order of preference.

Let me briefly define seven good voting systems, and briefly state a few of their main advantages. I’ll start with the two most briefly-defined and easily implemented voting-systems, and then discuss five rank-balloting voting-systems.

In voting-system discussion, the word “method” is used to mean “voting-system”, and that’s what I mean here when I say “method”.

1. Approval Voting:

Definition:

You can, by marking their names on the ballot, “approve” as many or as few candidates as you want to.

The winner is the candidate approved by the most voters.

Advantages:

1. You never have any possible reason to vote someone else over your favorite (That’s called the “Favorite-Burial-Critrerion” (FBC)–I’ll cite FBC for most of the other voting-systems here, as well).
2. The most easily-implemented. Doesn’t require any new software, balloting-equipment or new kind of ballots. The only change is 2 words added to the ballot-instruction: Where it now says “Vote for 1”, it would instead say “Vote for 1 or more”. Cost of change to Approval voting: Zero.
3. Approval is “Set-Voting”. You can vote any set of candidates, chosen by you, over the others, by approving only them.

2. Score Voting:

Definition:

You assign to each candidate a rating from 0 to 10, or from 0 to 100, etc.

The winner is the candidate whose ratings-total, among all the voters, is the highest.

Advantages:

Same as Approval.

The flexible ratings allow more expressivity.

3. Instant-Runoff Voting (IRV):

Definition:

You vote a ranking of candidates.

The Count:

Repeatedly, delete from all the rankings the candidate who currently tops the fewest rankings.

When one candidate tops most of the rankings, s/he wins.

Advantages & Disadvantage:

Has no chicken-dilemma.

IRV has some excellent properties, but it can eliminate the middle compromise, causing some people to rank that compromise over their favorite, to protect the compromise from elimination.

IRV shouldn’t be enacted unless people understand and accept that problem, and wouldn’t feel the need to rank someone over their favorite.

4. Bucklin Voting:

Definition:

Bucklin is Stepwise Approval. You vote a ranking. In each of successive “rounds”, each ballot gives a vote to each candidate that it ranks at the rank-level corresponding to that round.

For example, in the 1st round, each ballot gives a vote to each of its 1st-ranked candidate(s). In the 2nd round, each ballot gives a vote to each of its 2nd-ranked candidate(s)….etc.

If, in a round, one or more candidates gets a majority (a vote total greater than half the number of voters), then the one with the most votes wins.

If, when all the rankings have given votes to all of their candidates, no one has a majority, then the candidate with the most votes wins.

Advantages:

Meets FBC (defined above).

More stable than IRV. No unpleasant compromise-elimination surprises.

Was used in at  least 39 cities during the Progressive Era.

5. Benham’s Method:

Definition:

Do IRV until there’s an un-deleted candidate who pairwise-beats each one of the other un-eliminated candidates.

X pairwise-beats Y if more voters rank X over Y than vice-versa.

Advantage:

Shares IRV’s advantages, but always elects a candidate who pairwise-beats everyone else, if there is such a candidate.

6. Majority-Defeat-Disqualification Approval (MDDA):

Definition:

You rank, in order of preference, the candidates whom you especially want to elect (instead of someone else winning). You’re counted as approving every candidate that you rank, unless you expressly deny them approval.

The winner is the most approved candidate who doesn’t have another candidate ranked over hir by a majority.

Additionally, you have the option to indicate that you deny approval to any 1 or more candidates whom you rank.

Advantages:

1. Meets FBC
2. Has no chicken-dilemma problem.
3. Particularly good protection for higher-ranked candidates over lower-ranked ones. Especially for top-ranked candidates over all other ones.

Disadvantage:

Can fail “Mono-Add-Plump” criterion, meaning that the addition of a new ballot to the election can cause a candidate to lose, though he’d win without the addition of the new ballot—and can do so even if that ballot votes only for that candidate.

That’s a purely cosmetic “embarrassment criterion”, without any operational or strategic importance. It doesn’t cause any voting problem. But of course it has to be disclosed anyway.

7. MDDAsc:

Definition:

Same as MDDA, but with one additional rule:

For any pair of candidates whom you don’t rank, you’re counted as ranking each one over the other, with half of a vote. That’s what the “sc” in its name refers to. It stands for “symmetric completion” (of short rankings).

Advantage over MDDA:

Doesn’t fail Mono-Add-Plump.

Disadvantage compared to MDDA:

Less reliable protection of  higher middle-ranked candidates against lower middle-ranked candidates. (But still fully protects top-ranked candidates against everyone else.)

Protection of middle-ranked candidates against each other is less important than protecting all  ranked candidates against unranked ones, and protecting top-ranked against the others.

The matter of which of MDDA or MDDAsc you rank over the other depends on which you want more—Mono-Add-Plump, or more reliable protection between your middle-ranked candidates.

Here again is a link to the poll:
https://civs.cs.cornell.edu/cgi-bin/vote.pl?id=E_fa18e6840b070f44