[EM] Free riding

[Markus Schulze]

Hallo,

Juho wrote (31 Aug 2008):

 > Woodall free riding uses some irrelevant candidate that
 > is ranked first.
 >
 > Hylland free riding does not rank the favourite candidate.
 >
 > A third approach to free riding is to rearrange the
 > candidates to reflect the estimated probabilities.
 >
 > The true preference order of a voter is A>B>C>D>E>...
 > The voter expects A to be elected quite certainly.
 > Candidates B and C are less certain. The voter considers
 > B and C to be almost as good as A. Candidates starting
 > from D are considerably worse. As a result the voter
 > decides to vote B>C>A>D>E>...

Suppose that you expect candidate A to be elected quite
certainly. Then it is a useful strategy not to give your
first preference to candidate A. However, it is also clear
that it doesn't make any sense to rank candidate A below
candidates you despise.

Therefore, I would summarize your strategy as a Hylland
free riding strategy because you vote preferably for
those of your favorite candidates who are less assured
of election:

http://m-schulze.webhop.net/schulze2.pdf

Raph Frank wrote (31 Aug 2008):

 > I think this is the strategy that most parties actually
 > use for vote management.  They never recommend to the
 > voters not to rank a certain party member.

Actually, it is the main hypothesis of my paper that
Hylland free riding and vote management are actually the
same. In section 5.1 of my paper, I write:

 > Presumption of this paper is that the vulnerability to
 > Hylland free riding is that property of STV methods that
 > is misused in a vote management strategy. To be more
 > concrete: We presume that the term "Hylland free riding"
 > and the term "vote management" refer to the same
 > strategic problem. The only difference is that the term
 > "Hylland free riding" refers to this strategic problem
 > seen from the point of view of an individual voter who
 > tries to maximize the influence of his vote by voting
 > preferably for those of his favorite candidates who are
 > less assured of election, while the term "vote management"
 > refers to a political party or a group of independent
 > candidates that tries to maximize its number of seats
 > by asking its supporters to vote preferably for those
 > of its candidates who are less assured of election.

Markus Schulze