Single-member district

Single Member systems, also called Single Winner systems, elect a single winner. These can be combined into many single member systems run independently in districts to form a Regional System.

They can be classified by ballot type:

• Plurality Voting: A valid vote can choose only one candidate
• Approval Voting: A valid vote can only give a yes or nothing to a given candidate.
• Ordinal Voting: A valid vote can rank candidates 1,2,3... (Tied rankings are permitted in some methods but not others)
• Cardinal Voting: voting A valid vote allows independent numerical values to be associated with each candidate. (The set of valid values is limited.)

Classification

They can be sub-classified by different ways to aggregate the ballots.

Plurality Voting

There is only one way to combine plurality votes.

Approval Voting and Cardinal Voting

Since Approval is the degenerate case of Cardinal Ballots they have the same A sum would give the Utilitarian_winner while a median would give the majoritarian winner.

Ordinal Voting

Borda count and Instant-runoff voting are common aggregation methods

Single Winner Variations

Automatic Equal Ranking Line Option (AERLO)

A voter may mark a line in his/her ranking, meaning that if no one above that line wins, then that voter wants to promote to 1st place all of his/her above-line candidates and have a recount. (In pairwise-count methods the promotion only takes place if, additionally, there's a circular tie containing above-line and below-line candidates).

Automatic Truncation Line Option (ATLO)

A voter may mark a line in his/her ranking, meaning that if no one above the line wins, then that voter wants to drop from his/her ranking all of his/her below-line candidates and have a recount. (In pairwise-count methods the dropping only takes place if, additionally, there's a circular tie containing above-line and below-line candidates).