sequential runoff method (plurality with elimination)
TRANSCRIPT
Day 3 Sequential Condorcet and Approval
A
BCD A
B
C
DA
B
C
D A
BC
D
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1) Find the winner using Plurality. Is it a Majority?
2) Find the winner using Borda Count Method.
3) Find the winner using Instant Runoff.
Sequential Runoff Method (Plurality with elimination)
• Eliminates one choice at a time.• Eliminate the candidate with the least first
place votes.• Those first place votes get reassigned to the
person below.• Continue until you have a winner.
Day 3 Sequential Condorcet and Approval
Examples of Sequential Runoff Method
Sequential Runoff• Pros:
• Gets rid of the “worst” and gives the votes to others.
• Cons:• You can end up with a “tie” and not be able to finish the
method.
Day 3 Sequential Condorcet and Approval
The Method of Pairwise ComparisonEvery candidate is matched headtohead against every other candidate. Each of these headtohead matches is called a pairwise comparison. In a pairwise comparison between X and Y every vote is assigned to either X or Y, the vote going to whichever of the two candidates is listed higher on the ballot. The winner is the one with the most votes; if the two candidates split the votes equally, the pairwise comparison ends in a tie.
The winner of the pairwise comparison gets 1 point and the loser gets none; in case of a tie each candidate gets 1/2 point. The winner of the election is the candidate with the most points after all the pairwise comparisons are tabulated.
(Overall point ties are common under this method, and, as with other methods, the tie is broken using a predetermined tiebreaking procedure or the tie can stand if multiple winners are allowed.)
Ex.) Find the winner using pairwise comparison
Day 3 Sequential Condorcet and Approval
Condorcet Method
• Developed by Marquis de Condorcet
• Condorcet Method• The candidate that can obtain a majority over all other
individual candidates.• See how many times A beats B (is it a majority?) and A beats C,
etc. • If it is a majority every time, then that candidate is the winner.
• Pros• This person “truly” beats everyone else• Cons• Condorcet Paradox – No winner is found. Multiple candidates
have majority over others.
Day 3 Sequential Condorcet and Approval
More Examples with Condorcet
Practice – Complete with group and turn in!
• Which type of food is the plurality winner?
• Majority?• Borda Count?• Instant Runoff?• Sequential Runoff?• Condorcet?
Day 3 Sequential Condorcet and Approval
Day 3 Sequential Condorcet and Approval