Section 1: Social Choice Theory

Key Learning Points

• Discuss briefly the most familiar voting scheme, plurality.
• Define the formal model of social choice theory, considering other voting schemes.

Activities

1. Read section 9.1, section 9.2, and section 9.3 of the textbook;
2. Read the Tutorial on Voting Theory by Ulle Endriss.
3. Watch the following videos:
   1. Social Choice: Taste
   2. Social Choice: Voting Schemes
   3. Social Choice: Paradoxical Outcomes

4. Do the exercise: consider the following preference profile for 100 voters:

   33 agents: a > b > c > d > e
   16 agents: b > d > c > e > a
    3 agents: c > d > b > a > e
    8 agents: c > e > b > d > a
   18 agents: d > e > c > b > a
   22 agents: e > c > b > d > a

   Determine the winners according to plurality, Borda voting, STV, Copeland’s rule, and pairwise elimination (i.e., plurality with runoff).

5. Discuss the following question in the discussion forum: Can you construct a real-world example (different from the examples in the textbook) where the individual preference lists for three alternatives are as in the voting paradox of Condorcet?