Voting Methods Flashcards
What are the different voting methods I should know for the exam?
1) Plurality (with and without runoff)
2) Borda Count
3) Condorcet Winner
4) Approval Voting
5) Copeland’s Rule
What is a Condorcet winner?
A candidate who beats every other candidate in a one-on-one election
What is a Condorcet loser?
A candidate who loses to every other candidate in a one-on-one election
What is the plurality rule?
Each voter selects one candidate (or none if voters can abstain) and the candidate with the most votes wins (Also called first past the post rule)
What is a major problem of the plurality rule?
It can elect a condorcet loser
What is the quota rule?
1) Candidates have to pass a certain threshold (counter to electing a condorcet loser)
2) Majority rule: quota with q = 0.5 (50%)
3) Unanimity: quota with q = 1 (100%)
What is an upside and a downside to ranking methods?
Upside: much more expressive
Downside: ranking every candidate can be very demanding
What is the borda count method?
1) Each voter provides a ranking of the candidates
2) Then a score is assigned to each candidate: n-1 points for the candidate ranked first, n-2 for second, etc.
3) The candidate with the highest score wins
What is a scoring rule?
Any method that calculates a score based on weights assigned to candidates according to where they falli in the voters’ rankings
What is the approval voting scoring method?
1) Gives 1 point to each candidate that is ranked in position k or higher, and 0 points to all other candidates
2) 1-Approval voting is the same as plurality rule
Do ranking and scoring rules guarantee a concordet winner?
No
What are multi-stage elections?
successively removing candidates that perform poorly in the election until there is one candidate that is ranked first by more than 50% of the voters
What is the plurality with runoff method?
1) Start with a plurality vote to determine top 2 candidates
2) If a candidate is ranked first by more than 50% of the voters, then that candidate is declared the winner, if not there is a runoff between the top two
What is voting by grading?
We allow different candidates to be assigned the same grades
What is negative voting?
Each voter is allowed to choose a candidate to vote for OR against (give the candidate -1 points)
