Which voting system is the best? - Alex Gendler

Summary

The script explores various voting systems to determine the fairest way to decide the location of a new spaceport on Mars. It critiques plurality voting, instant runoff voting, and the Condorcet method, showing how each system can lead to unfair outcomes. The script highlights how different voting methods can give some groups more influence, ignore minority preferences, or encourage tactical voting. Ultimately, it suggests that no voting system can perfectly balance fairness in elections with more than two choices, due to conflicting assumptions about what fairness means.

Takeaways

• 🗳️ Plurality voting, or 'first past the post,' lets each individual cast a single vote, but often results in outcomes that most voters may dislike.
• 📊 In the example given, West Base wins easily under plurality voting, but this is considered the worst result for the majority of colonists.
• 🔄 Instant runoff voting allows voters to rank choices, eliminating the lowest-ranked options in rounds, but still leads to questionable results, as seen when East Base wins despite being unpopular.
• ⚖️ Tactical voting can manipulate runoff voting systems, with voters supporting a less popular option in early rounds to skew results in their favor.
• 🤔 The Condorcet method involves head-to-head matchups between all options, with the winner being the option that wins the most pairwise contests.
• 🏅 North Base wins using the Condorcet method, as it is a central location and doesn't rank last for any group, demonstrating fairness in certain scenarios.
• 🔄 However, the Condorcet method can fail in specific situations, such as when preferences create cycles (A > B, B > C, C > A).
• 📐 There are numerous voting methods, each with unique mechanics and potential for unfair outcomes depending on the situation.
• ⚠️ Mathematical proofs show that no voting system can perfectly satisfy all fairness criteria in elections with more than two choices.
• 💡 The way votes are counted in a democracy has significant implications on who benefits, and fairness depends on the method used.

Q & A

What is the scenario used to introduce the concept of voting in the script?

The script introduces the scenario of building a new spaceport on Mars at one of four recently settled Martian bases, where a vote is being held to determine its location.

What are the four Martian bases mentioned, and how many colonists live in each?

The four bases are West Base with 42 colonists, North Base with 26 colonists, South Base with 15 colonists, and East Base with 17 colonists.

Which voting method is described as the 'most straightforward solution,' and what does it entail?

The 'most straightforward solution' is plurality voting, or 'first past the post,' where each individual casts a single ballot, and the location with the most votes is chosen.

Why is plurality voting considered unfair in this scenario?

Plurality voting is considered unfair because, while West Base wins easily due to having the most residents, it is the farthest from the other bases, making it the worst result for most colonists.

How does the instant runoff voting system work, and what was the result in this scenario?

In instant runoff voting, voters rank the options, and the option with the fewest first-place votes is eliminated, with those votes reallocated to the voters' next choices. In this case, East Base ultimately won, despite initially being in second-to-last place.

What is the issue with using the instant runoff voting system in this scenario?

The issue with instant runoff voting is that it can result in a base winning even though a majority of voters ranked it among their two least preferred options, as happened with East Base.

What is tactical voting, and how did it affect the outcome in the multiple rounds voting system?

Tactical voting occurs when voters cast their votes strategically rather than honestly to influence the outcome. In this scenario, East Base residents voted for South Base in the first round to prevent North Base from advancing, leading to South Base winning despite being the least populated.

What is the Condorcet method, and how is it applied in this scenario?

The Condorcet method involves voters expressing preferences in every possible head-to-head matchup. The option that wins the most head-to-head comparisons is the victor. In this scenario, North Base won three matchups, while South Base won two, making them the most central locations.

Why is the Condorcet method not considered an ideal voting system?

The Condorcet method is not always ideal because it can fail to select a winner in cases where preferences are cyclical, such as when voters prefer A over B, B over C, and C over A.

What conclusion does the script reach about finding a fair voting system?

The script concludes that it's impossible to design a voting system that doesn’t violate at least some theoretically desirable criteria when there are more than two options, highlighting that fairness in voting is more complex than simply counting votes.