Given that CES and EVC both now have multi-pronged grading systems for voting systems, I figure I want to share what my own goals for a voting system are, and in particular why I do not back IRV or Distributed Voting.
Most of these are practical in nature. I do not consider failing, say, monotonicity as inherently bad; it is only bad if it causes a legitimate problem, like making it unsafe to support your favorite candidate.
So… here are my goals:
1. Diversity of Opinion
Many people do not like either the Democratic or Republican parties. Personally I have issues with both, but much stronger issues with one of them than the other and so I usually vote lesser of evils.
Approval Voting has the nice advantage that I can support multiple candidates. This means you can start having several candidates run within a party. This is important because you can have, for instance, pro-climate Republicans or pro-gun Democrats, creating more of a meritocracy of ideas.
This also reduces the influence of money, because while it may be strategic to approve one frontrunner and disapprove the other, there are still other candidates who can pull ahead of both.
Score Voting and STAR voting improve on this because one can punish, say, a Republican who wants to end Social Security or a Democrat who wants to let incarcerated felons vote, without having to send them down to zero.
IRV ostensibly would let you rank all the candidates of your party up top. But it can eliminate candidates in the wrong order, and we all know (e.g. from the Yee diagrams) that IRV has an extremist bias. This could even lead to IRV pitting the two extremes against each other, or your side’s extreme with the other side’s moderate (i.e. you lose). Worse yet, IRV ignores your second preferences when deciding which candidate to eliminate.
DV fixes the second problem but only partially solves the first.
- Approval: B
- Score: A
- STAR: A
- IRV: D
- DV: C-
- FPTP: F
2. Resistance to Manipulation
We all wish our voting systems would work as well as we want, but of course voters and candidates will game the system.
Obviously none of these systems can get an A because every system can be manipulated somehow.
- Score gets a B. I do not actually see that much wrong with strategic voters back-sliding the system to Approval because Approval is a pretty good system and the extra benefits of Score are still there if you want to use them. The system also resists money and strategic nomination rather well.
- Approval gets a B as well for resisting money and strategic nomination. There is less room for voter strategy, but I think whatever strategy does exist will lead to, at worst, the election of the Condorcet winner.
- STAR gets a B-. The minus is just because it is very vulnerable to tactical voting (it fails NESD*) and strategic nomination in 3-candidate elections, but the first effect goes down as the number of candidates increases. The worst that runoff-gaming can do in large elections is degenerate the system into Score Voting which is a pretty good system, although if some ideology cannot run 2 candidates then that does put them at a disadvantage. Still, I expect this to be minor because STAR always elects either the Score winner or the Score second-place who should still be a pretty good candidate.
- DV gets a D just because it is too opaque for me to really figure out how to manipulate it. But this “security through obscurity” is a bad idea and I need to punish it with a low score.
- IRV and FPTP get an F for well-known reasons.
3. Practical Use
- IRV: D. IRV has been used before to successfully declare winners, but it still requires a lot more infrastructure to count centrally and has the problem of recounts in early stages dramatically affecting the eventual winner.
- DV: F, because in addition to IRV’s silliness, DV is very complicated for the average voter to understand.
- STAR: B. STAR gets knocked down a bit because the runoff step requires a bit of creativity to successfully count without centralizing it. Then again, there are only 2 rounds (not many as in IRV and DV) and it only requires O(n^2) to precinct count.
- Approval and Score: A+. No real problems here. In fact since they are compatible with each other and Approval is compatible with IRV, I give them a bonus.