Jameson Quinn wrote (28 March 2010):
>/ What does "MCV" stand for? />/ /
Ooops. I garbled your term, didn't I? It's supposed to be Majority
Choice Approval, not Majority Choice Voting.
"Majority Choice Approval" was invented and introduced a few years ago
by Forest Simmons, and I think he
coined the term.
For a short time I endorsed it as something simple that meets Favorite
Betrayal, the "voted 3-slot ballot version"
of Majority for Solid Coalitions and Mono-raise.
>/ Does "top-two runoffs" mean a second trip to the polls? />/
/
Yes. I regard this as an advantage. If the situation is divisive
enough to prevent a majority choice in two rounds of approval,
then a further period of campaigning is a healthy thing. It's the only
way to guarantee a majority. (I don't think that mandating
full ranking counts as a true majority).
/ />/ How are the candidates scored to determine the top two? Is it
based on the //candidates' scores after the second
> Bucklin round? >
// /That's the simplest answer, and I'd support it. It's also the best
answer with honest voters. Actually, the best answer for
discouraging strategy is to use the two first-round winners. That
tends to discourage strategic bullet voting, since expanding
your second-round approval can not keep your favorite candidate from a
runoff.
Unfortunately these top-two runoff versions break MCA's compliance with
Favorite Betrayal and Mono-raise.
Top-rating your favourite F could cause F to displace your compromise C
in the runoff with your greater-evil E, and then F loses
to E when C would have beaten E.
Also, like plain Approval followed by a runoff between the two most
approved candidates, it is *very* vulnerable to "turkey-raising"
Push-over strategy. Voters who are fairly confident that their favourite
can get into the final runoff have an incentive to also approve
(or top-rate, depending on the version) all the candidates they are
confident their favourite can pairwise beat in the runoff.
The Push-over incentive is stronger than it is in normal TTR, because
the strategists don't have to abandon their favourite in the first
round (and so taking a much greater risk, if there are too many trying
the strategy, of their favourite not getting into the final without
their votes when without their strategising their favourite would have
got into the second round and won it).
Also some people might object that parties that run a pair of clones
have an advantage over parties that run a single candidate.
From your (Jameson's) earlier (26 March 2010) message, I gather you
consider "likely to elect the CW" a big positive.
For something simple then, why not "3-slot Condorcet//Approval"?
*Voters give each candidate a Top, Middle or Bottom rating. Default
rating is Bottom.
If one candidate X (based on these maybe constrained ballots) pairwise
beats all others, elect X.
Otherwise, interpreting Top and Middle rating as approval, elect the
most approved candidate.*
Chris Benham
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