1. If every voter prefers A over B, the electorate prefers A over B
2. If no voter changes preference between A and B, the electorate's preference of A and B is unchanged
3. No single voter can always change the electorate's preference
[1]: https://en.wikipedia.org/wiki/Arrow%27s_impossibility_theore...
This actually isn't true, because major party candidates will be worse off, but I think he meant something like Hicks-Kaldor efficient, or positive sum.
I am also seeing several comments that try to take into account the preferences of the candidates themselves, or their parties. Why? Aren't we talking about efficiency from the perspective of the electorate? To the extent that the candidates are themselves members of the electorate, and can vote for themselves, shouldn't we ignore them in this analysis because their preferences are inherently biased?
I fully agree with you. I was just being precise in my usage of Pareto efficiency, which includes all agents in a situation. Especially because it's used so often when Hicks-Kaldor improvement is meant (which means that there's the possibility for Pareto improvement after redistribution of gains).
As an impractical example, if you could get every voter to tell you exactly how many utils a particular candidate is worth to them (maybe through complex incentives), as a quantity and not as a ranking, you would end up with a perfect voting system.
As a more practical example, approval and range voting don't fall victim to Arrow's theorem.
Would end up with a perfect system, or could end up with a perfect system? I assume that latter, because I can easily design a system that uses that extra data and is far from perfect.
Assuming could, not would, my question then is that known? Or is it just known that Arrow's theorem does not apply to such systems, and so we cannot rule out that such a system could be perfect?
See here:
https://www.reddit.com/r/badeconomics/comments/5a9a1b/arrows...