What Makes A Voting Method Good?

Aaron Hamlin
9 min readOct 1, 2018

You’re probably familiar with voting methods generally; that is, how voters add information to their ballots and how that information is calculated. Right now, our main voting method has us choose one candidate, and the candidate with the most votes wins. This is called plurality voting or first-past-the-post voting but here, we’ll refer to it as our current “choose-one” voting method.

However, this is not the only way to vote. Some voting methods have us score, rank, and even approve multiple candidates. That information can be used to calculate average support, simulate sequential runoffs, translate rankings to point values, or run pairwise comparisons between candidates like a round-robin tournament.

Given all the possible voting methods with their infinite iterations, how do we know whether a particular one is any good?

Here are some guidelines.

A Good Winner

What’s a “good winner”? Here’s one definition: A good winner is the candidate who makes the most voters happy.

You can measure this directly in polls by asking respondents to use an honest assessment scale that has them indicate how much they would like to see each candidate elected. Then, take responses from this scale and average them.

If you’re short on real-world election data, you might try using a computer simulation to evaluate a voting method. A simulation can generate millions of elections. The simulation can set different dynamics — such as tactical voting prevalence and candidate number — for each simulation to show which kinds of winners a voting method chooses. You can see what the results look like on average and the variability among those winners.

These high-utility winners are consensus candidates who appeal to the largest breadth of voters. They hold appeal for the bulk of voters while not marginalizing large electorate segments. They are good winners.

Another good winner, however, might be someone preferred to all other candidates by more than half the voters. This is called an absolute majority winner, and these…