[EM] Amalgamation details, hijacking, and free-riding

[fsimmons at pcc.edu]

----- Original Message -----
From: Jameson Quinn 
Date: Wednesday, August 3, 2011 4:10 pm
Subject: Re: Amalgamation details, hijacking, and free-riding
To: fsimmons at pcc.edu
Cc: election-methods at lists.electorama.com

> 2011/8/3 
> 
> > So if the true preferences are
> >
> > 20 A>B
> > 45 C>?
> > 35 (something else),
> >
> > the C supporters could spare 21 voters to vote A>C so that the 
> amalgamated> factions would become
> >
> > 41 A>C
> > 24 C>?
> > 35 (something else) .
> >
> > I can see where it is possible for such a move to payoff, but 
> it seems
> > fairly innocuos compared to other
> > strategy problems like burial, compromising, chicken, etc.
> >
> 
> Not to me. I would be livid to find out my vote had been 
> hijacked. All the
> other strategies you mention at least use a voter's own vote.
> 

"Highjacking" sounds bad, but it is just one form of "over-riding" votes.  At least it doesn't over-ride your 
first place preference like the compromising incentive twists your arm to do.  Every method eventually 
over-rides various preferences at some point in the process.  Compromising is a form of extortion that 
blackmails you into expressing a false preference. That's the most egregious form.
 
In other words, compromising forces you to either lie or lose.  If somebody else highjacks, they lie to 
take advantage of you, but with much more risk than the liar who buries to take advantage of the CW 
supporters.
 
For this kind of highjacking to work, the highjacking faction would have to have more than three times the 
support of  the highjacked faction, as can be seen from the above example (which lacking that much 
support in the hijacking faction gives an obvious first place advantage to A).  That kind of superiority is 
more than enough to over-ride pairwise wins in ranked pairs, river, beatpath, etc.