Hot off the presses! SRV-PR!

Depends on how many seats there are.

I don't think anyone's going to propose PR with fewer than 3 seats.

Thank you for posting this. An important criterion for evaluating a single-winner system is how well it serves as a stepping stone to PR, and I was about to ask what SRV-PR would look like.

The formula for ballot influence is given as “1 / (1 + sum/max)”. I assume “max” refers to the maximum permissible score, which I believe has been 9 or 5 in most of your examples. If so, I recommend that you instead use the maximum permissible score that the voter in question actually gave to a candidate. If for example the highest score a particular voter gives to any candidate is 4, then for that voter, “max” would be 4.

The reason I’ve found for doing this (there might be others) is that otherwise a large bloc of voters who all hate an important minority candidate can deliberately underscore their preferred candidates. Depending on various factors like the size of the bloc, this underscoring could let them elect their preferred candidates while still hogging ballot influence for the runoff elections so as to block the hated minority candidate.

One fundamental characteristic of PR is that there’s no effective way to vote against someone you don’t like. (This goes hand in hand with minorities being able to elect candidates.) Instead, you focus on voting in favor of the people* you do like, and then it’s their job to go be effective legislators or whatever, advancing things they're in favor of and blocking things they're not. Presumably, having a two-candidate runoff of any kind undermines this characteristic (and therefore means the system qualifies as semiproportional rather than full PR); but as long as each voter makes use of their maximum score, the “ballot influence” mechanism should compensate somewhat. I haven’t looked at this thoroughly.

*Or for parties you like, in some implementations of PR.

An important criterion for evaluating a single-winner system is how well it serves as a stepping stone to PR

This assumes that PR has been shown by empirical evidence to produce the most utilitarian policy. But that has not been shown.

I recommend that you instead use the maximum permissible score that the voter in question actually gave to a candidate.

You have to be extremely careful proposing rules like this. Historical efforts to counter such strategies have been shown to cause more problems than they solve. For instance, you might kill the proportionality theorem that RRV satisfies.

The history of voting methods is littered with attempts to "fix" existing systems by introducing various semi-random ideas like this, and then not vetting them with math PhD's. Mark kind of got lucky on his Score Runoff Voting idea in that it still manages to perform well. That's usually not the case.

If you want to read up on the state of the art in PR theory, I'd check out this page.

https://www.youtube.com/watch?v=oSNNav2eYwk

This assumes that PR has been shown by empirical evidence to produce the most utilitarian policy.

No it doesn't. I was stating an opinion, and my personal concept of what is valuable in a voting system doesn’t automatically match yours.

The history of voting methods is littered with attempts to "fix" existing systems by introducing various semi-random ideas like this, and then not vetting them with math PhD's.

What I’ve done here is (1) point out a problem and (2) suggest a fix. And sure, I readily believe that in your experience, most of the so-called fixes people suggest are not helpful. So back up a step and look at the problem: SRV-PR can be thought of as having two mechanisms -- the scoring and the runoff -- through which voters exercise clout. I’ve pointed out that a voter can sacrifice their scoring clout to get extra runoff clout, and I’ve implicitly opined that this is bad. (And now I’ll opine it explicitly: This is bad.) SRV-PR advocates should be aware of this and decide whether they care. If they do care, they should do some thinking about possible solutions, including the one I proposed.

Hah! It was luck, buddy. You couldn't have known for sure until Jameson tested it for you.

I blame Rob Richie, since he's the one who really came up with it. I'm just a good listener ;-).

I was stating an opinion, and my personal concept of what is valuable in a voting system doesn’t automatically match yours.

This isn't subjective. Elections have objective effects on human welfare.

Clay: Correct me if I'm wrong, but it sounds like you're saying there's one true method of voting system evaluation, and if that particular method rates system A higher than system B, then everyone is supposed to agree that system A is better. Well forget that. People are individuals, and we have opinionated disagreements on what characterizes a good voting system just like we have opinionated disagreements on almost everything else.

To your other comment: Obviously elections have effects on human welfare, but could you please clarify what you mean by “objective” and how it relates to my holding the opinion that an important criterion for evaluating a single-winner system is how well it serves as a stepping stone to PR?

(If http://www.icasualties.org/ is accurate and I’m interpreting it correctly, 418 US soldiers died in Operation Enduring Freedom/Afghanistan in the year 2011. That’s a big change in human welfare that, yes, was affected by a considerable variety of elections that have taken place over time. Possibly including, to give one example, Richard Nixon’s election to congress in 1946, which may have affected his becoming president in 1969, which may have affected William Rehnquist being nominated to the supreme court in 1971, which may have affected George W. Bush becoming president in 2001, which may have affected the existence of Operation Enduring Freedom and its casualties in 2011, three years after Bush was replaced by the winner of yet another election. Are you speaking of an objectivity that can be discerned, or one that’s based in a hypothetical omniscience?)

Of course, all this is a sidetrack. My main point is that in SRV-PR, a voter can sacrifice their scoring clout to get extra runoff clout. I think SRV-PR advocates ought to care about this; and if they do care, they should do some thinking about possible solutions, including the one I proposed.