[EM] SODA sometimes FBC-safe

Jameson Quinn jameson.quinn at gmail.com
Thu Mar 1 14:01:09 PST 2012

2012/3/1 MIKE OSSIPOFF <nkklrp at hotmail.com>

>  Jameson:
> You wrote:
> Actually, with SODA, it does help, because you can know ex ante (by
> looking at the predeclared preferences) when you are safe by FBC. That is,
> if you prefer A>B, and B prefers A, or A prefers B, or A and B both prefer
> a certain viable C, then you are safe. Only if B prefers the most-viable
> third candidate C, but A is indifferent between B and C, then you might
> consider a favorite-betraying vote for B. And even then, it's only
> appropriate if A very nearly, but not quite, is able to win... not exactly
> the situation where favorite betrayal is the first thing on your mind.
> This is a specific enough circumstance that favorite-betraying strategy
> would never "take off" and become a serious factor in SODA.
> With SODA, you can give that as a solid ex-ante guarantee to most voters,
> just not quite all of them. This is unlike the situation in most voting
> systems, where you can make no solid guarantees before the vote unless you
> can make them to all voters.
> [endquote]
> Ok yes, as you say, that's a very different situation from the ordinary
> FBC-failure, because, for most people there is known to be no
> favorite-burial need. The favorite-burial problem really
> exists when there's uncertainty for everyone, or for a large percentage of
> the voters, which isn't the case with SODA.
> Thank you.

By the way, I left out one further circumstance in which you are FBC-safe.
Using the letters above, you are also safe if C declared a preference for
B. If C prefers A or is indifferent between A and B, then you might have to
worry (if all the other circumstances listed above also pertain.)


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