All of snafuy's Comments + Replies

Okay, I accept your point that a cooperating 40% group will beat three non-cooperating 20% groups with unrelated interests in pretty much any voting system. That doesn't change whether A+B+C are physically incapable of communicating, or they lack sufficient trust to make an agreement stick, or there is a law against voting agreements that they are following (and Y+Z are not), or something else. So it's not the case that QV is vulnerable to collusion/cooperation when other voting systems are not. I think the remaining debate is whether QV is more vulnerable, or vulnerable in a worse way. I'm not sure what the answer is to that. (I'm not brgind or EdgyCam, I can't speak to what they meant)

tl;dr: I disagree. Other than first-past-the-post, which is terrible, 3 non-cooperating 20% groups with similar preferences will and should beat a co-operating 40% group. This is also true for quadratic voting. Here is a detailed scenario matching your 40/20/20/20 example. Suppose we have the following voters: * Alice prefers apples to other fruit, and strongly prefers fruit to vegetables. * Bob prefers bananas to other fruit, and strongly prefers fruit to vegetables. * Charlie prefers cherries to other fruit, and strongly prefers fruit to vegetables. * Yasmine prefers yams to other vegetables, and strongly prefers vegetables to fruit. * Zebedee prefers zucchini to other vegetables, and strongly prefers vegetables to fruit. Y and Z are able to coordinate. A, B, and C are not. This is not because Y and Z are more virtuous, nor because vegetables are better than fruit. It's for the prosaic reason that A, B, and C do not share a common language. All voters have similar utility at stake, for example Charlie is not allergic to yams. In a first-past-the-post voting system, with apple, bananas, cherries, yams, and zucchini on the ballot, Y and Z can coordinate to gets yams and zucchini on alternating days. This is good for Y and Z, but does not maximize utility. However, in a (good) ranked voting system, we instead get a tie between apples, bananas, and cherries, which we break randomly. This is good for A, B, and C. Proportional representation would get a similar result, assuming that the representatives, unlike the voters, can coordinate. Approval voting would get a similar result in this example. Quadratic voting calculations are a bit harder for me, and I had to experiment to get a near-optimal voting strategy. Let's suppose that A votes as follows: * $30 for Apples (+5.48) * $15 for Bananas (+3.87) * $15 for Cherries (+3.87) * $20 against Yams (-4.47) * $20 against Zucchini (-4.47) B and C vote similarly but according to their own preferences. Naive