[EM] Free riding

[Juho]

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>...

This strategy increases the probability of B or C to be elected. If B  
and C are not elected the vote goes to A (not lost in the case that A  
needs more votes since it gets less votes than expected (due to  
strategic voting or for other reasons)). It is possible that B or C  
gets elected while A will not, but the risks are not too big. In any  
case the three clearly best candidates (A, B, C) will get all  
possible power of this vote. There is also no risk of the vote going  
to some irrelevant candidate (as in Woodall free riding).

This generalizes to any preference order, not only to the handling of  
the first favourite. The voter can estimate the probabilities of all  
candidates to become elected (also taking into account the impact of  
strategic voting) and the rearrange the whole preference list based  
on the estimated probabilities and the personal utility of each  
candidate.

The resulting strategic preference order could resemble that of  
Woodall free riding if there is a candidate that very certainly will  
not be elected. The utility of that candidate may be quite low.

The resulting strategic preference order could resemble that of  
Hylland free riding if the probability of the favourite candidate is  
very high. That candidate would however be listed somewhere close to  
the end of the list.

Juho




		
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