1. Electoral Systems

2. Evaluations of electoral systems Fairness = Proportionality? California statewide vote for seats in the House of Representatives: 43% R 54% D California distribution of seats in the House of Representatives: 38% R 62% D

3. Evaluations of electoral systems Level of satisfaction? Number of losers? Fairness = Proportionality? Representation Simplicity

4. Consequences of Electoral Systems

5. How do electoral systems affect the behavior of candidates and voters? Party systems “Duverger’s Law”: The more proportional the system, the greater the number of “effective” political parties there will be.

6. Why Duverger’s Law Mechanically Psychologically (candidates) Psychologically (voters)

7. Evidence for Duverger’s Law Electoral formula“Effective” # of political parties USAPlurality1.95 AustraliaMajoritarian2.5 NepalPlurality2.4 CanadaPlurality2.7 UKPlurality2.2 BelgiumD’Hondt8.54 NetherlandsD’Hondt5.14 AustriaLR Hare3.54 GermanyLR-Hare3.31

8. Evidence for Duverger’s Law

9. How do electoral systems affect the behavior of candidates and voters? Party systems Party organization Election campaigns

10. The American System Seats not allocated proportionally Constituency based representation Simple ballot choices Two large coalitional parties Decentralized parties Decentralized campaigns

11. Median Voter Theorem Assumptions: Single dimensional issue space Pairwise vote Voters always vote (no abstentions) Voters have one unique preferred position Voters’ preferences “single peaked” Parties/candidates maximize chances of winning Preferences are normally distributed in electorate

12. Median Voter Theorem If all voters vote and their preferences are single-peaked and on a single dimension, then the median ideal preference can defeat all other positions in a pairwise vote.