Plurality with elimination, Runoff method, Condorcet criterion

Plurality with Elimination

1. Each voter votes for one candidate.2. A candidate that receiving the majority

of the votes is declared the winner.3. If no candidate receives a majority of the

votes, then the candidate/candidates with the fewest votes is dropped from the ballot and a new election is held.

4. You follow this process until a candidate receives a majority of votes.

Example6 7 5 3 9 3

1st C A C A B D

2nd A C D D A A

3rd B B B B D C

4th D D A C C B

Run – off Method

You only keep the top two first place voters and have an election between those two.

Example8 9 5 4 2

1st C E B A A

2nd A D C D C

3rd B B E B B

4th E C A C D

5th D A D E E

Condorcet Criterion

If candidate X can defeat each of the other candidates in a head-to-head vote, then X is the winner of the election.

Say you have candidates:A,B,C,D

First say A vs. B if B winsThen try B vs. C if B wins

Then try B vs. DHowever, if C won in step 2 then you have to

go back and check C vs. A and C vs. D

ExampleA A A B B C C

B B B C C B B

C C C A A A A

Assignments

Classwork – Pg 33-35 27 (a,b,c, Run-off), 20 (a,b, Run-off), 31, 33 (a,b, Run – off)

Homework - Pg 33-35 28 (Run-off), 30 (Run-off), 32, 34 (a,b, Run – off)