1. Voting
Fairness

2. Fairness
T. Serino
If you haven’t noticed by now, elections are for more than just electing our president or our mayor. Elections of various kinds can play an important role in our lives. Choosing the right “representative” whether it be for a political office, president of a school club, a company logo, the MVP of a league, or the site of the next Olympic Games is very important to various groups of people.
Because of its importance, we strive to use voting systems that are FAIR.

3. Fairness The Majority Criterion The Condorcet Criterion
T. Serino
We have discussed some weaknesses in the voting systems we’ve learned throughout this topic. To decide which systems are most fair, we use four specific criteria called the “fairness criterion.”
The four fairness criterion are:
The Majority Criterion
The Condorcet Criterion
The Monotonicity Criterion
The Independence-of-Irrelevant-Alternatives Criterion (IIA)

4. Fairness
T. Serino
Both the Plurality method and the Plurality with Elimination method will always satisfy this criterion.
Unfortunately, the Borda Count method and the Pairwise Comparison method can both violate this criterion.
Does not necessarily violate the criterion

5. Fairness
T. Serino
(Head-to-Head criterion)
Pairwise comparison is the only method studied that is guaranteed to satisfy the Condorcet Criterion.
Plurality, Borda Count, and Plurality with Elimination Methods can all violate the Condorcet Criterion.
Does not necessarily violate the criterion

6. Fairness
T. Serino
Plurality Method is the only method studied that is guaranteed to satisfy the Monotonicity Criterion.
Borda Count, Plurality with Elimination, and Pairwise Comparison can all violate the Monotonicity Criterion.
Does not necessarily violate the criterion

7. Fairness
T. Serino
Unfortunately, every voting method studied can violate the IIA Criterion.
Does not necessarily violate the criterion

8. Fairness
T. Serino
In 1949, mathematical economist Kenneth Arrow showed that it is actually impossible for any democratic voting method to simultaneously satisfy all of the fairness criterion.
Ironically, making decisions in a consistently fair way is inherently impossible in a democratic society.

9. Fairness
T. Serino
Note: Although this table makes the Borda count method seem to be the worst method, Borda count is considered to be one of the most fair methods covered.

10. athematical M D
ecision
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