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CATEGORIES:Isaac Newton Institute Seminar Series
SUMMARY:A quantitative version of the Gibbard-Satterthwait
e theorem - Kindler\, G (HUJI)
DTSTART;TZID=Europe/London:20110401T113000
DTEND;TZID=Europe/London:20110401T123000
UID:TALK30513AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/30513
DESCRIPTION:Consider an election between q alternatives\, wher
e each of the voters rank the different alternativ
es\, and the winner is determined according to som
e predefined function of this voting profile. Such
a social choice function is called manipulable\,
if a situation might occur where a voter who knows
the rankings given by other voters can change her
ranking in a way that does not reflect her true p
reference\, but which leads to an outcome that is
more desirable to her. \n\nGibbard and Satterthwai
te proved that any social choice function where mo
re than two alternatives can be selected is manipu
lable\, unless it is a dictatorship (where the out
come of the election only depends on the choices o
f one voter). In the case where the social choice
function is neutral\, namely when it is invariant
under changing the names of the alternatives\, we
prove a lower bound on the fraction of manipulable
preference profiles which is inverse polynomial i
n the number of voters and alternatives. Our proof
in fact does not rely on discrete harmonic analys
is - finding an analytic version of the proof woul
d be the role of the audience. \n\nJoint work with
Marcus Isaksson and Elchanan Mossel.\n
LOCATION:Seminar Room 1\, Newton Institute
CONTACT:Mustapha Amrani
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