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Properties of Voting Systems:

Properties of Voting Systems: . Independence of irrelevant alternatives Pareto condition monotonicity manipulability. Describe the property of independence of irrelevant alternatives (IIA). . Given: Candidate A is a winner over Candidate B in an election.

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Properties of Voting Systems:

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  1. Properties of Voting Systems: • Independence of irrelevant alternatives • Pareto condition • monotonicity • manipulability

  2. Describe the property of independence of irrelevant alternatives (IIA). Given: Candidate A is a winner over Candidate B in an election. IIA Property: If a second election occurs and one voter changes his/her ballot, but doesn’t change his preference of A versus B, then Candidate A should still be the winner.

  3. The Borda Count doesn’t satisfy the property of independence of irrelevant alternatives. Let’s examine the following results: Find the winner using Borda scores.

  4. What is Pareto’s Condition? If everyone prefers one choice or candidate (A) over another candidate (B), the latter candidate CANNOT be a winner. Examine the table below. What method doesn’t satisfy Pareto’s Condition?

  5. What is monotonicity? What voting method was monotone? Monotonicity is a property that applies to an election with 3 or more candidates. Given: Candidate A is a winner over Candidate B. If a second election is held and the only ballot change is for a voter to move the winning candidate A higher on his/her ballot, then the original candidate, A, should still be the winner. Find the winner below using Hare Elimination.

  6. What is Manipulability? A voting system is manipulable if a voter can submit a ballot that misrepresents the voter’s true preferences. The ballot is said to be insincere or disingenuous. It is also referred to as strategic voting.

  7. Pizza Voting – Again! Pretend you would sincerely would rank five pizza options in order of favorite to least favorite as: Pepperoni Sausage Ham Mushroom Broccoli You decide you REALLY want the pepperoni and are worried it may not get the most 1st place votes. How can you vote strategically or manipulate the pizza election when you cast your ballot?

  8. HOMEWORK: Exercises p. 364- 367, # 9, 16, 18, 27 Copy the preference schedule tables, and yes, explain in a few SENTENCES!

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