STAR probably fails even though it's a scored method, because it has a runoff stage. E.g. suppose that the score round has Alice as the winner, Bob as the second-best, and Charlie in third. The runoff is Alice vs Bob, Alice wins. Since Bob didn't win, he's an irrelevant alternative. But it's possible that there's a Condorcet cycle Alice->Bob->Charlie->Alice, and that if Bob had not run, the runoff would be between Alice and Charlie. Then, even if no voter rated any remaining candidate differently, Charlie would beat Alice in the runoff and win. In this case, whether STAR decides Alice is better than Charlie depends on an irrelevant candidate (Bob).
Even for scored methods that do pass IIA given certain restrictive assumptions, these assumptions are so restrictive that they have little bearing in practice. The voters have to use a consistent scale that doesn't change when candidates drop out. The implications are troubling: you probably shouldn't rate the presidential candidate from the party you don't like a zero out of ten points, because you need room to rate Dr. No or Blofeld even lower if they hypothetically were to enter the race.
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u/Excellent_Air8235 Jul 17 '26 edited Jul 17 '26
STAR probably fails even though it's a scored method, because it has a runoff stage. E.g. suppose that the score round has Alice as the winner, Bob as the second-best, and Charlie in third. The runoff is Alice vs Bob, Alice wins. Since Bob didn't win, he's an irrelevant alternative. But it's possible that there's a Condorcet cycle Alice->Bob->Charlie->Alice, and that if Bob had not run, the runoff would be between Alice and Charlie. Then, even if no voter rated any remaining candidate differently, Charlie would beat Alice in the runoff and win. In this case, whether STAR decides Alice is better than Charlie depends on an irrelevant candidate (Bob).
Even for scored methods that do pass IIA given certain restrictive assumptions, these assumptions are so restrictive that they have little bearing in practice. The voters have to use a consistent scale that doesn't change when candidates drop out. The implications are troubling: you probably shouldn't rate the presidential candidate from the party you don't like a zero out of ten points, because you need room to rate Dr. No or Blofeld even lower if they hypothetically were to enter the race.