The Supplementary Vote alternative?

In reviewing the extensive entries about the recent UK electoral system referendum, which had been posted at the LSE blog on British politics over the past year, I was struck by Professor Patrick Dunleavy’s claim that the Supplementary Vote would have been a fairer system to propose. The Supplementary Vote (SV) is another form of “instant runoff,” and thus bears considerable affinity to the Alternative Vote (AV)–the option that actually was put up against the status quo in last week’s referendum (and was defeated resoundingly).

Under SV, voters are allowed to give just two preferences. If no candidate has a majority of first-preference votes, then all candidates in the contest other than those with the top two totals of first preferences are eliminated. Second choices are then redistributed among the top two, and the candidate with the most votes at this stage is elected.

This procedure differs from AV in at least two fundamental respects. First of all, under AV the voter may (or if we are talking about the Australian House of Representatives, must) rank all the candidates, not just two. Second, AV is a sequential elimination method. Rather than eliminating all but the initial top two, it eliminates the weakest candidate at each stage of the count, up until a winner has been determined. AV thus emulates, in one “instant” act of ballot-marking, the sequential processes used in many political parties and legislative institutions to choose a leader, rather than the two-round majority rules used to elect many national presidents, as does SV. ((Intermediate variants are also possible. For instance in some US jurisdictions that have adopted forms of instant runoff, voter preferences are restricted to the top three. The counting process in these jurisdictions typically otherwise follows the AV approach, rather than that of SV (as far as I know; there may be exceptions).

There is also the so-called Contingent Vote, which allows voters to express more than two preferences, but shares with SV the immediate elimination of all but the top two candidates if none has a majority. Thus the Supplementary Vote and the Contingent Vote arguably have more in common with one another than either has with the Alternative Vote, although the Contingent Vote is less likely to waste votes of those who gave their second preference to an already eliminated candidate. (A form of the Contingent Vote seems to be what Sri Lanka uses to elect its president.) ))

SV is used to elect the London mayor and those of some other English cities; it is used nowhere to elect legislators that I know of.

In a post from last summer, Dunleavy stated:

The London form of AV also has the great advantage that it creates a run-off between the top two candidates in a local constituency – only one of them can win.

I must admit to having a hard time understanding why this is a virtue for a ranked-ballot method. If the race has two clear front-runners and one or more also-rans, fine. The two systems would produce the same result, and such a result would be “fair” by almost any standard, I should think. However, if there is uncertainty about the top two as the election day looms, SV poses a real problem for voters. Not only must they know their two top preferences (easy enough), but they must also think strategically about them (potentially a challenge). If one’s first preference is likely to place third or lower, then one must be careful that one’s second preference will clear the initial top two. Otherwise, the second preference will not be counted, as it will have been wasted on an eliminated candidate. By contrast, under AV, if your second preferred candidate has been eliminated, the counters look to your third (and so on).

But isn’t SV a truer (instant) runoff, inasmuch as it is a top-two system? Here is where the instant-ness ceases to be an advantage. In an actual two-round system of majority runoff, the top two choices of the electorate as a whole are revealed before the voters must give their second preference (i.e. before voters whose initial choice was eliminated in the first round decide which of the two remaining candidates to support in the runoff). The risk of a relatively more extreme candidate winning would be greater under SV than under either AV or two-round majority: if more moderate voters lost their second preferences by tending to have cast them on the third-place candidate, relatively more extreme voters may elect, by less than 50%, their preferred candidate. I have no idea how common this would be in practice, but it seems it would be a not implausible effect of SV. In an actual second round, under this scenario, the voters can “update” and vote for the less extreme of the remaining candidates in the runoff. ((I recall this point being addressed somewhere in the political science literature; apologies for not having a citation.))

Given the substantial number of UK constituencies in which there is a close race between second and third, SV would seem to be clearly less fair than AV to voters confronted with strategic choices about estimating which two candidates are the top two of the electorate at large. (By the way, it is also the case that in presidential elections by two-round majority, the gap between the second and third candidates tends systematically to be less than that between the top two, suggesting that SV would indeed be a poor choice for these elections.)

I fail to see why a case could be made that SV is fairer, especially in any setting in which the “Duvergerian” tendencies of an existing FPTP (plurality) system have already broken down–which are pretty much the only situations in which it would be considered in the first place.

25 thoughts on “The Supplementary Vote alternative?

  1. For the failings of the Supplementary Vote, researchers should note the Doncaster Mayoral Election of 2009. Here, Labour and Conservative candidates were competing against two candidates with extreme nationalist views, and three independents – one supported by the Liberal Democrats.

    The first round ended in a near dead-heat, the leading independent had 22.9%, one of the nationalists 22.6%, the third-place Labour candidate 22.3%. The far-right vote combined effectively, the mainstream preferences were lost (barely two-fifths of votes could be redistributed), and Doncaster’s elected mayor came from the hitherto-unknown English Democrat party.

    In this election, the voters of Doncaster were asked to guess who would come in the top two if their initial preference didn’t. Almost a third of voters guessed wrongly, and didn’t influence the final result.

  2. Thanks, Weaver. That was exactly the sort of scenario I was getting at, but I had totally forgotten that it actually happened in Doncaster.

  3. I just thought of an idea. Voters should receive a preferential ballot. You have a first choice and a runoff choice.

    For example, 2000 U.S. Presidential Election. If you voted for Nader in the first round, you have the following runoffs to vote in: Bush v. Gore, Bush v. Buchanan and Gore v. Buchanan.

    My proposal would be this:

    – Each voter will be required to cast a first choice and a runoff choice
    – If a candidate gets an absolute majority in the first round, the race ends
    – If not, the top 2 candidates would qualify for the runoff, while the other candidates are eliminated
    – In this case, if a voter voted for Nader in the first round, their vote would be transferred to Gore, Buchanan and Gore, depending on the runoff

  4. In fairness to Dunleavy, his definition of “better” appears to be “more winnable”. Specifically, “accepted by London voters in 1999 by more than two to one, and invulnerable to 90 per cent of the distortions flung at AV by the successful ‘No to AV’ campaign.” (I haven’t tried to evaluate the latter claim.) That leaves him enough wiggle room to accept all of MSS’s (completely justified) criticisms of the Supplementary Vote and still claim it is “better”.

    The problem with Dunleavy’s argument is that the Supplementary Vote might well have lost too. First, opponents would not have had to make up distortions to fling at it; they would have had a number of perfectly valid points. More important in my view, whatever else they were doing, voters were punishing the Lib Dems. Voting against the Supplementary Vote would have served that purpose just as well as voting against AV.

  5. What is so bad about non-instant runoffs again?

    I realize it is expensive to hold a second vote, and that turnout drops from the first vote, but I think the additional information voters get in the extra weeks of campaigning (with different campaign strategies as candidates themselves gain the additional information about the electorate revealed by the first round results) is worth it. And its a much more intuitive sell than the various forms in non-instant runoffs, to the point where they are even used in the US. People are familiar with the idea of overtime in sports after all.

  6. As Antony Green has pointed out, standard AV has elected one of the top 2 candidates in all but 7 Aust House of Reps races since 1918 (with compulsory full preferences), and in all but one single race since NSW adopted optional preferences in 1981 (and Qld followed in 1992). IOW, in only a handful of cases has a candidate won from 3rd place or lower.

    However, if we summarily exclude all but the top 2, we re-introduce tactical voting in the form of “squeezing”, and create the risk of a France 2002 result where a “majoritarian” system gives a worse result, from a majoritarian point of view, than two successive plurality votes (with no elimination) would have done.

  7. @Ed

    Leaving aside the transaction costs, although they are significant, a delayed run-off cannot deal with the Chirac/Le Pen problem. In the French presidential election in 2002 the 3 leading candidates had 19.88%, 16.18% and 16.8%. In the second round Chirac received 82.21% against the extreme right’s Le Pen.

    AV would have allowed mainstream candidates to accumulate votes and pass Le Pen. The electorate would not have been forced into a ridiculous second round where they had to choose between a president who had just secured less than 20% of the popular vote and a candidate whose program was unacceptable to the vast majority of the electorate.

    The functional equivalent to AV is not a second round of voting but an unlimited number of rounds where the single trailing candidate is excluded at each round. That would have avoided Le Pen in the last round, but would also have required at least 11 rounds of voting.

  8. The French presidential election in 2007 also showed that there are still elements of tactical voting in two-round elections. Left-of-centre voters had to decide whether they thought Royal or Bayrou would have the best change of beating Sarkozy in the second round. And there were no more than three viable candidates – an increase of only one compared to a one-round system.

  9. It would seem that wins from third place would be somewhat more common in the UK than in Australia due to the nature of the party system at the time of implementation (in the hypothetical case of a yes vote in the recent referendum).

    For reasons referenced by some previous comments, that would clearly be an argument in its favor, relative to Supplementary Vote, Contingent Vote, or a two-round majority system.

    Nonetheless, when I look at national-level figures for Australian votes by party in the 1930s and 1940s (e.g. 1934) I wonder why wins from third place were not more common. I can only surmise that the third and fourth parties’ strengths were more localized than today’s UK LibDems. Or perhaps it comes down to preference-swapping in two blocs, such that there was not a real third force in these elections. If that is the case, it would tend to support the claims of the pro-PR opponents of AV in the UK who see the promotion of a two-bloc party system as a feature (and a flaw) of AV.

  10. At least since the emergence of the Liberal Party in 1944 Australian politics has tended towards a two-bloc system. The interesting feature was the appearance of two successive bridge parties. The Democratic Labor Party a Catholic split from the Australian Labor Party, tended to siphon enough votes from the ALP to keep it out of power for a generation. Strangely enough the Australian Democrats, in origin a split from the Liberals, then siphoned votes back towards Labor, contributing mightily to the election of the Hawke-Keating Labor governments. Both parties tried to stay away from directly becoming part of a bloc, although both were closer to one side than the other.

    You also have an interesting move by some state branches of the Nationals to move out of the Liberal-led bloc, while other branches are merging with the Liberals.

    The Greens do not have a bridge role and will become a genuine test case for the emergence of a party outside the two-bloc system.

  11. Is this assertion true that the Greens are not a bridge party? Many Green Parties around the world can’t be fitted in a classic left/right paradigm.

    The Greens were elected in Melbourne because of Liberal preferences. Maybe the Green party is a bridge to the Liberal Party albeit probably the Libertarian side of the Liberal Party.

    The Green party could become the equivalent to the Labour Party, as the National Party is to the Liberals. The Green Party is an Urban Inner City Party, and the National Party is the rural party.

    You also have to remember that although 80% of Greens preference flow towards Labour, at least some Green votes flow toward the Liberals.

    The problem with preferential voting is that some people assume that all the votes will flow toward one candidate, but preference flows may flow toward different candidates.

  12. The DLP and the Democrats enabled disaffected voters from one party to park their first preferences on their way to the opposite bloc. There is very little evidence of Coalition voters moving to Labor by way of the Greens.

    Rather, Labor at present seems to be losing electors in both directions, to the Greens on their left and the Coalition on their right. The recent NSW election was an exception where the electorate seems to have been determined to defeat Labor no matter what.

    Recent Labor tactics rely on the theory that they ‘own’ the progressive vote and need to re-assure conservative voters in a small number of marginal seats. It does not seem to be working all that well.

  13. I’ve been looking at ballot designs. There’s one that I like alot.

    Say you have a ballot for President 2000. You have Bush, Gore, Nader and Buchanan. Now, under a normal structure, you’d either have squares where you rank the candidates or columns for a first choice, second choice and third choice.

    But, I find this one interesting. How about a ballot like this:

    For example:

    1st choice Bush
    +No 2nd choice ___
    +2nd choice Buchanan+No 3rd choice ___
    +2nd choice Buchanan+3rd choice Nader ___
    +2nd choice Buchanan+3rd choice Gore ___
    +2nd choice Nader+No 3rd choice ___
    +2nd choice Nader+3rd choice Gore ___
    +2nd choice Nader+3rd choice Buchanan ___
    +2nd choice Gore + No 3rd choice ___
    +2nd choice Gore+3rd choice Buchanan ___
    +2nd choice Gore+3rd choice Nader

  14. Derek, that would work fine with fewer than four candidates. But with as many as 9 or 10 (not unknown in Australian IROV-AV elections), it would become massive through combinatorial explosion.

  15. Tom, you make a great point! OK, this idea for a ballot design is a tad too much. How about IRV with 3 columns? A voter can mark a first choice and second choice with an x or 1 or 2. But the third column would require a voter to rank the candidates from 3 on. Of course, the voter could mark an x in the third column but that would mean that this x vote is the same as a 3.

  16. Derek, what are the advantages to limiting preferences to 3? Ballot design needs to maximise information to the voters and maximise their chance to make their choice effective. Why require them to fill out squares in columns when they could write a simple number beside the candidate’s name?

  17. Alan, my guess is – so voting machines can read it.

    Mind you, since 1990-91 Australia Post has used machines that can read numbers in the postcode (ie, four-digit zip code) squares on envelopes. Am not sure why they don’t use these to read ballot-papers. It would speed up the count (and also reduce the ratio of BS to truth in No2AV’s propaganda from 10:1 to 9:2).

  18. I’m not limiting preferences to 3, only the columns. The first choice and second columns would require a 1 or an X or a tick. However, the third column, which would be for alternate preferences, could allow people to put a number 3,4,5, etc. next to the candidate’s name or just put an X next to the candidate’s name, as if this were a third choice. I’m not in favor of restricting preferences, quite the contrary but if in the third column you place an x next to a candidate, that would assume that it would be your third preference. If you put the number 3,4,5, etc. next to a candidate, it’s different.

  19. Derek, I’m sorry, I may be misunderstanding something but I just don’t see the advantage. I do see a massive disadvantage asking people to write Xes in 2 columns, Xes to do one thing in a third column and numbers to something else in the same column. It seems to me to be a butterfly ballot writ huge.

  20. Ok, Alan, here’s what I’m trying to say. I propose a three-column ballot. You have a column for the first choice, a column for the second choice and a column for alternate choices.

    Now, in the first 2 columns, a voter may mark a preference by either putting a number, marking an x or marking a tick.

    In the third column, voters would have to put a number.

    It’s not that hard for voters to consider at least 2 candidates.

  21. Derek, why? What is the advantage? And why ask the electors to vote by different methods in the first 2 columns and in the third? Why 3 columns and not 1? Or 17?

  22. Derk, it seems to me to be a complication for the sake of a complication. Again I do not see the advantage and I see large disadvantages in terms of voter confusion.

  23. Alan Renwick, at his Facebook feed, notes regarding Eurovision:

    Under AV, Azerbaijan won by 20 votes to 19. Under FPTP, Bosnia would have won on 5 votes.

    …under supplementary vote, Italy wins over Bosnia by 9 votes to 6.

    Actual Eurovision rules are a form of Borda Count. Azerbaijan won.

  24. OK, here’s one idea.

    Voters rank their candidates in order of preference. The ballot is separated into 2 columns: top choices and bottom choices. Another detail: in each column, you rank the candidates in order of preference. So, in a 4-way race, instead of getting a ballot with one column where you rank your candidates 1,2,3 & 4, you get a ballot with two columns, and in both columns you rank the candidates 1 & 2, that’s it!

    Let’s say in a 4-way race, you have Gore, Bush, Nader and Buchanan running. A Nader voter would fill out both columns the following way:

    Top choices

    1st Nader
    2nd Gore

    Bottom Choices

    1st Bush
    2nd Buchanan

    In order for a candidate to get a majority, it must not only get a majority of the 1st top choices but also not get the most votes of the last place bottom choices.

    When eliminating candidates, when considering top choices, the candidate with the least votes is out; when considering bottom choices, the candidate with the most votes is out.

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