Score voting: a simpler, less distorting measure of voters’ will

Score voting avoids the vagaries and gaming that are intrinsic to preference ranking systems. It is simpler and more reliably reflects the will of voters. You have probably used it if you have completed a survey. We should use it in political elections.

The 2018 Victorian election has turned up another result in which ‘preference whispering’ by minor parties has distorted the will of the people ($, William Bowe at Crikey), if we take the will of the people to be indicated by first-preference votes.

Minor parties scored 25% of upper house seats from 20% of first-preference votes, whereas the Greens scored only one seat with votes that exceeded almost all minor-party votes individually. In one case a primary vote of 1.3% beat a Greens primary vote of 13.5%.

A senate election in WA a few years ago hung on the chance flow of minor preferences halfway through the count. A slightly different flow would have swung the count to a different winning candidate, though the key preferences were not directly about that candidate.

Voting systems in some states and federal elections were reformed a few years ago to reduce this kind of distortion. The trouble is there is no perfect preferential voting system. Preferential voting is intrinsically prone to such distortions. There is even a mathematical theorem proving it can never be guaranteed to accurately reflect the will of the people.

There is however another voting system that is much less prone to distortion, and to the associated gaming commonly used to deflect voters’ intentions. It is called, variously, score voting, range voting or utilitarian voting.

You have probably used this system, just not in elections. It is used commercially to measure the popularity of products. It is also commonly used to determine voters’ approval of the performance of prime ministers and other politicians, and sometimes to choose among different policies.

This is the kind of survey in which you might be asked, about each alternative, whether you approve, disapprove or don’t care. The surveyor assigns a score to each option, such as +1, -1, and 0, and simply adds up the scores for each alternative. Sometimes the scale is extended to include strongly approve (+2) and strongly disapprove (-2).

So in an election a ballot paper would list all the candidates and ask you to rate each candidate. You could assign your score or degree of approval to any or all candidates. The candidate with the highest tally of scores would be the winner. If there were, say, five candidates to be elected then the five highest scorers would be elected.

This system has many advantages, the main one being it is simple and only minimally distorts the will of voters. There would be little opportunity to game the system because there are no flows of preferences that can be manipulated, simply a tally of scores.

There would be no such thing as an informal vote, because if you did not rate a candidate it would be taken to mean “don’t care”.

If you were equally comfortable with two candidates, you could give them both your full approval, and they would both benefit. If you wanted to maximise the chances of one candidate, you could give them maximum approval and all the others maximum disapproval. Conversely if you wanted to minimise the chances of a candidate you could give them maximum disapproval and all the others maximum approval.

There would be another important benefit. If all parties were very unpopular, as has been true in Australia for some time, then that would show up in the scores. For example a winning candidate might get an average score of only -1, and the other candidates -1.5 or less. In that case it would be clear that voters had chosen the least undesirable candidate, rather than one of whom they really approve.

Winning politicians love to claim they have a mandate for all their policies. It’s never that simple of course, but with this system you would have objective evidence they had not been “approved”, just tolerated as the least-worst alternative.

There is a web site that explores the details and nuances of score voting, run by the Center For Election Science in the US. One version, in which you simply either approve or disapprove, is called approval voting.

Technically it is called a cardinal voting system, as distinct from an ordinal voting system. You rate each candidate rather than putting all candidates in rank order. You can express your absolute level of approval, not just your “approval” of a bad candidate relative to worse candidates.

So let’s have ballot papers that survey our rating of candidates, elections that simply and straight-forwardly choose the highest-rated, or least-low-rated, candidates, and results that register our collective degree of approval or disapproval.

7 thoughts on “Score voting: a simpler, less distorting measure of voters’ will

  1. Julie Clutterbuck

    Geoff, it seems like this system (for, say, the Victorian upper house) would effectively disenfranchise minor parties.

    Let’s say we have four major parties that have primary votes of roughly 40, 40, 10, 10% (under current system), running for an electorate with 5 members. I claim a fair outcome would be two members from each major party with the fifth from one of the minor parties.

    If everyone “approves” all candidates from their first-choice party, and only those candidates, then we get 3 from one major party and 2 from the other.

    Major parties would probably run campaigns encouraging their supporters to vote like this.

    But we’d expect a vote spread not as black-and-white as that. Firstly, if you primarily support a minor party, then you probably should pick your preferred candidates from your closest major party and boost those above their running mates. This has the good outcome that candidates are encouraged to seek support outside their primary bases (I hate the idea of a “base”, but you get the picture… Labor candidates would seek votes from Green voters etc).

    But what would it take to get a minor party candidate elected? They get their own 10% of approvals, but need around 40% to be competitive with the major parties. A Greens candidate would need 3/4 of the Labor voters to approve of them, (less if they also got approvals from other groups). This seems implausible, especially for a person at the beginning of their careers without strong name recognition (Bob Brown at the end of his career might get in with this, but not at the beginning).

    The approval system seems to suit centrists– which is in some way a good thing, because it encourages compromises– but we’ve also seen that a lot of good can come from having people who are not part of major parties in parliament, with new ideas from the fringes.

    I can also see why this would be a good idea for places with voluntary voting, tending to counteract the polarisation that we see emerging from those systems.

    You already observed that every system has its weaknesses. The main problem in Victoria is that in the past we’ve relied on the decoherence of preferences to ensure that a high primary vote got a proportionate outcome. Abolishing group voting tickets (or requiring preferential above-the-line voting) should return us to that.

    Hope you are doing well! It’s been a long time.



  2. Julie Clutterbuck

    On second thoughts, an even better thought experiment is to think of just two main parties, one with 60% support and the other with 40%. If most people approve of the candidates from a single party, then we end up with winner takes all.

    On the other hand, maybe this system would encourage popular centrist independents (like Phelps or Windsor), and people would feel happy voting for their own personal slate, from across parties…


    1. Geoff Post author

      Hmm, perhaps you’re right Julie. It avoids the distortion of micro parties gathering preferences but swings too much the other way.

      Perhaps you could try your thoughts on the web site mentioned. Felix (above) from there has already commented here. They seem to have debated it a lot.

      Yes it’s been a while, hope you’re all doing well. In Melbourne. I’d be happy to hear more by regular email, geoffd at netspeed dot com dot au .


      1. Felix Sargent

        If you’re looking to elect a multi-member organization you’ll want to use a system of proportional voting.
        Proportional Approval Voting uses a weighting system which “uses up” a voter’s ballot as their candidates get elected.

        Any proportional representation system will work to ensure that minority parties are adequately represented. Whether it’s Approval or Score or not is subject to academic debate.


  3. Geoff Post author

    The proportional approval voting described in Felix’ link above is conceptually a bit tricky (you want voters to understand how their vote will count) and admitted to be computationally intensive, as all combinations of result have to be checked to see which one yields maximum voter satisfaction.

    The key idea it that the weight of a voter’s vote decreases according to the number of successful candidates they have already supported with a vote.

    Perhaps a far simpler system with a similar rationale would be to discount the accumulated scores of successive members of the same party, say by 20%. Then the score of the fourth member of a party would be discounted to 51.2% of its raw value, giving other parties a better chance. A bit of detailed design work could find plausibly reasonable discount values in a particular context, such as the Australian Senate system.



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