[EM] Majority-Judgement. Condorcet.

[Kristofer Munsterhjelm]

On 02/02/2012 09:40 PM, MIKE OSSIPOFF wrote:
>
> MJ:
>
> Thanks for all the answers about MJ strategy.
>
> But I'd told how easily a strategic faction can take advantage of and
> beat a sincere-voting faction.
>
> And, if the contest is close, then even a small difference in sincerity
> could decide which faction's candidate wins.
>
> And that amounts to a co-operatioin/defection problem too.
>
> No amount of speculation or discussion of MJ's other strategy issues or
> mystique will make that go away.
>
> Thanks, Kristofer, for confirming my conjecture: MJ strategy is like RV
> strategy.

Don't forget the rest that I said, though. Maximal MJ strategy is like 
RV strategy. A Homo Economicus would vote Approval-style in a one-shot 
election. He might do so even when he thinks there are going to be 
elections after this one -- or he may not (as Jameson Quinn says).

In any event, I think that MJ provides enough protection, were the 
majority's default sentiment to vote honestly, that they would not feel 
the need to vote strategically simply to head off a worse outcome. 
Furthermore, if there is some amount of strategy going on, the voters 
don't have to go all the way to a maximal ballot to defend their 
outcome. All they need to do, in order to support X over Y, is to vote X 
and Y on the other side of their respective medians. As the fraction of 
strategists goes to unity, the exaggeration needed goes to the maximum 
possible.

Thus, if the voters aren't rational economic men (and turnout is 
evidence in itself that they aren't), the voters default to honesty 
(i.e. don't reason like Warren did), and the parties can't push large 
swathes of the people to vote strategically, then you shouldn't need to 
vote Approval style in an MJ election.

In other words, in an MJ election, there's a certain room for honesty. 
If you get past this headroom, then you should vote somewhat 
strategically. If you get further past it, you should vote more 
strategically still. But as long as you're in the first area, then you 
have to get a lot of your friends to vote strategically too to make a 
difference.

So the whole thing hinges on whether people will vote strategically even 
though they may not benefit over voting honestly. It's like a 
multiplayer prisoner's dilemma where, if some fraction f all defect, 
they get a greater payoff and the rest gets a sucker's, but if a 
fraction less than f tattles, they get the same payoff as if they 
hadn't. Would ordinary people defect? I don't think so, if f were large 
enough, because people are decent (i.e. not Homo Economicuses).