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 winners tend to coincide with utility winners. The catch? This “majority winner” may not always exist, and runoffs only artificially create majority winners.

Another example of a good winner is a Condorcet winner. This is a winner who can beat every other candidate head-to-head. (Imagine a round-robin tournament with an undefeated winner; that’s the idea.) Like a majority winner, a Condorcet winner doesn’t always exist. When they do exist, they also tend to be the high-utility winner as well.

Practically any voting method can pick a good winner in easy situations. If there’s a clear winner with more than 50 percent of the vote, any voting method will likely get the winner right, including our current choose-one voting method.

But elections don’t always play out in easy mode. What we’re really interested in is a voting method that does the job in complex situations. We’re talking about 4- to 5-way races or elections with similar candidates who could potentially split the vote. If the election is close, or has multiple candidates, under the current choose-one method, you may not even know who the best candidate was. That’s because that voting method doesn’t capture the information you need to see whether the winner was a high-utility or Condorcet winner.

We obviously want to make sure the voting method picks a good winner, like the examples above. If a voting method fails at this — particularly if it does so badly — then it’s not worth considering. After all, selecting a good winner is a voting method’s core job. But there’s more to look at in practice than whether a voting method is good at electing a strong candidate. That’s particularly true if you’re looking at multiple voting methods that perform well in the winner-selection area.

Minimizing Complexity

There are different ways to measure complexity. One is how easy it is to explain how the voting method works. Do people understand not just how to fill out the ballot but also how the voting method calculates that information? Or, at the very least, do people understand the general concept for how the voting method works?

However, the way a voting method calculates voter data comprises most of its complexity. That’s particularly true with multi-winner proportional methods. There, voting methods tend to use complicated reweighting and partial ballot transfer schemes. While some of these calculations are easier than others, this complexity is often just a price we pay for good proportional methods.

Ballot complexity can directly interact with the voting method and the number of candidates running. For instance, ranking candidates can be mentally demanding when you have a candidate list of 10 to 20 candidates. You could sometimes see 10 candidates in a highly competitive election with only one winner. But for a multi-winner election with five or more winners, like a city council, a voter could easily see dozens of candidates. At that point, ranking becomes impractical and an alternative like proportional approval voting, where you select candidates rather than rank them, becomes more appealing.

Ballot complexity can also present itself through ballots that are filled out incorrectly, called spoiled ballots. Ranking methods in particular tend to have more spoiled ballots and can be an indicator of voter confusion. There, voters may improperly give some candidates the same ranking or another mistake causing the ballot not to count.

Encouraging Competition

A voting method should act as a temperature gauge for all the candidates, not just the winner. For the voting method to succeed, the following factors need to be fulfilled:

Factor one: expressiveness. If a voting method doesn’t allow the voters to express any information, then you don’t even have a starting point. Forcing voters to choose only one candidate, for example, is the least information a voter can provide. Unsurprisingly, this doesn’t provide sufficient information to assess all the candidates, mainly because the voter was never given a real opportunity to say anything about the candidates to begin with.

Factor two: tactical voting. Tactical voting is when voters purposefully put down inaccurate information on their ballot to maximize their ballot’s likelihood of having a personally favorable impact on the outcome. Tactical voting is an unavoidable aspect of voting methods. So even if we can’t eliminate tactical voting, we’d still like to minimize it.

Factor three: using the information. Just because a voting method takes in ballot information from the voter doesn’t necessarily mean that information is actually used. For instance, instant runoff voting, a ranking method, only uses first choice preferences at any one point and only counts next-choice preferences if the candidate being ranked is eliminated for having the fewest first-choice preferences. If the next-preferred candidate on a ballot has already been eliminated, then support for that candidate doesn’t appear on any tally. And if a candidate isn’t eliminated, then the support for the other ranked candidates on that ballot also don’t appear on any tally. This means the support for other candidates can go unmeasured and remain invisible.

Some of these voting method dynamics like inexpressiveness or haphazard ballot data use can cause a voting method to be susceptible to vote splitting. Vote splitting means that support divides between similar candidates so that candidates are shown with less support than they actually have and it can cause candidates not to run for fear of being labeled a “spoiler”. This was Michael Bloomberg’s rationale for why he didn’t run in the 2016 U.S. Presidential election.

We see that how candidate support is gauged can affect how candidates are perceived. It can even determine whether certain candidates run. And the last thing we want to do is create a barrier to entry for candidates that is too high. In democracy, competition is good, and a good voting method should encourage it.

Administrating the Vote

For many reasons, the software behind voting machines in many states is inadequate. This means more complicated voting methods require new software and new machines. If modern software isn’t an option, then you’ll have to stick with a simpler system. Some cities experience years’ long delays implementing alternative voting methods due to not having proper software. At a certain point though, those delays become inexcusable.

If hand counts are preferred, then a voting method’s complexity will become an issue. That’s particularly true for a voting method that requires ballot transfers over rounds. This kind of complicated voting method is certainly not impossible to run by hand, but the labor involved is significantly more compared to other methods.

If a voting method’s administration requires tallies at the local precinct level rather than a central location, then this can also create problems. Not all voting methods are precinct summable due to how votes are tallied. Instant runoff voting, for instance, requires all votes be tallied in a central location since it requires ballot transfers.

Other methods may technically be precinct summable but require more labor. For instance, STAR voting uses scores with a single runoff between the two candidates with the highest scores. This means that to get precinct summable tallies, administrators must compile both scores and pairwise comparison tallies between all candidates translated from scores. And this must done in every precinct. While possible, this may be a tall order for some areas where the administration has limited sophistication with alternative voting methods.

Risk-limiting audits should really be the standard for elections to ensure their integrity but they aren’t. They use statistical sampling techniques to determine whether to do a recount. If these audits were the norm, then different forms of data, such as that found in ranking methods, could create complications. This becomes particularly challenging with instant runoff voting. That’s because the multiple rounds create additional opportunities for different outcomes. The situation is even worse in instant runoff voting elections where which candidate is eliminated in each round is close.

Ideally, we’d like to think we can just throw software at the problem. But in the real world, this doesn’t always work out.

Representation

In executive offices, like mayor or governor, representation is more straightforward. In other conditions, this can be more complicated. For instance, if you have a legislative body or council, then you may wish to have that body be more diverse. One way to deal with that is to use a multi-winner proportional voting method. That is, you’re electing multiple candidates simultaneously. The voting method then elects candidates in proportion to the number of people that supported them.

Electing councils or legislative bodies only makes up a portion of situations, but it shouldn’t be ignored. Ignoring these types of elections can inadvertently have us exclude key groups. For instance, choosing as many candidates as there are seats to be filled can exclude entire segments of the electorate. Additionally, ignoring how multi-person bodies are elected opens us up to gerrymandering.

If we want a legislative part of our government to cover broad ideas, then we need to have a voting method that elects a diverse enough body that can actually generate those broad ideas. That kind of diversity goal is fundamentally different than the goal with single-winner elections since there what a “best” candidate looks like is relatively more straightforward. Still, we need to make sure a multi-winner voting method doesn’t give any group more than their fair share of seats.

Good Voting for Good Winners

A voting method isn’t good or successful merely because it’s been around a long time. Saying that an election completed “without a “hitch” is also poor evidence. In uncompetitive scenarios with only two candidates, which voting method was used won’t matter. Sadly, this uncompetitiveness describes most U.S. elections. What does matter is how a voting method performs under tighter elections with many candidates and whether the voting method encourages that competition to begin with.

In the end, a voting method must be good at electing good winners when electing executive offices, and it must provide fair representation to multi-person governing bodies. But it must also consider practical elements like the sophistication of software, administrators, and the electorate itself. Finally, a good voting method must accurately gauge candidate support so that it can foster the type of competition currently devoid in our elections.