STV & the Labour Party

STV & the Labour Party

There’s a sudden revival of interest in STV as the LP adopts it as a means of electing the CLP reps. There are in my mind, three problems with STV for party managers and one for voters. The fact that “order” can be critical in the results is important. When combined with the degree of discipline within Party voting blocs and the propensity to bleed votes from the block, getting the quota early is of advantage to parties. The problem of avoiding having large numbers of your votes trapped in the losing quota is also critically important for party managers particularly if the quota is high.

The Order based nature of STV counting leads to a series of well-known problems with STV in that it is one of the easier systems to game and has a number of design features which encourage manipulative or gaming behaviour. STV is not monotone, participative, consistent nor does it meet the No-Betrayer criteria.

There is no strategy that can compensate for a bloc’s voters not voting for all the candidates in the slate. Even within the activist or membership layer, many are more committed to their faction than to the Party, which may lead people to desert their first choice slate for another as the individual candidates become distasteful to the voter. I am curious if we could model the effect this ‘bleed’. The speed of desertion may well be determined by the slate construction as some on the slate might be exceptionally unacceptable to the otherwise loyal electorate. We should also note that not transferring reduces the quota[1] and so is equivalent to a (part) vote for all remaining candidates and acts as de-facto vote in favour of the highest remaining contender.

Early success militates against having votes lost in the losing quota, particularly as the STV transfers surpluses before eliminating candidates.

If running a complete slate, the offer of a recommendation to support as a second choice is not worth so much.

The disadvantage to voters is that their optimal strategy may not involve voting in a straightforward way as it may be best if someone likely to pick up a lot of transfers is eliminated before the transfers occur. This is more acute in instant run-off elections and depends on whether they want a candidate to win or prefer that others lose.

I can’t see what to do about weak discipline. If we take the example of the UK where we have Labour, the Greens, the Lib Dems and the Tories, we can see how people, who’s first choice might be, say, Labour might switch to the Green list after one or two votes for what ever reason and the Greens might go in both directions to Labour or to the LibDems. The system is designed to have this effect.


[1] This is the failure to meet the Participation Effect. …

Voting Systems Theory and STV

Voting Systems Theory and STV

It is important to understand that a bunch of clever people have thought hard about voting systems; we don’t have to invent this. I remember that our management in Sun Professional Services tried to imbue us with the mantra, “Innovate, Don’t Reinvent” and others have declared that the process of innovation is standing on the shoulders of giants. Voting system qualities known as criteria have been defined. There may be some as yet undiscovered criteria, but it would be best if we debate the pro’s and con’s using an agreed categorisation and science.

One has to be brilliant to be both in a minority and right, and most of us are not that brilliant.

Wikipedia, on their article, Comparison of Electoral Systems, says this,

Attitudes towards systems are highly influenced by the systems’ impact on groups that one supports or opposes, which can make the objective comparison of electoral systems difficult. … To compare methods fairly and independently of political ideologies, voting theorists use voting method criteria, which define potentially desirable properties of voting methods mathematically.

Wikipedia – Comparison of Electoral Systems

One thing we should note is that not all criteria can be applied to all systems, the key differences are between single winner systems, and multiple winner systems and then between list based and non-list based systems.

While some consider and seek to judge instant run off elections, sometimes referred to as the Alternate Vote as a special case of STV i.e. an STV with only one winner, the fact that there is only one winner makes it a separate and quite different system. This is shown by the fact that it passes and fails different voting criteria. Also, in AV elections, there is no transfer of a surplus votes and the minority i.e. the wasted voted can be as high as 50% – 1. This is better than simple plurality systems where the losing proportion can easily be quite high majorities. It seems to me that one critical goal of democratic voting systems should be to ensure that the “wasted” or losing votes are as small as possible.

Some criteria only apply to singe winner elections, and while it’s hard to game an STV election, it is not impossible. Games can be played by candidate/parties or by voters. STV’s problems come from the fact that surpluses and eliminations occur in an order and thus transfers are impacted by this ordering.

The Wikipedia article tests STV against 7 voting systems criteria and fails it on five. Some of the criteria seem to be remarkably similar and, it seems to me, all relate to honesty and motivation in voting behaviour and how the voting system reflects this honesty. STV fails the Monotonicity Criterion as there are cases where you can support your preferred candidate by down ranking them. It fails the Consistency criterion, probably by design and I am not sure it’s all that desirable, but this is about sub-set aggregation which can’t be done in STV, Participation, that your voice is always stronger if you vote, and “No favourite betrayal”, where you have no incentive to vote for anyone other than your favourite.

It’s certainly not perfect but we should learn from thinkers that have gone before us.  …

New Blood, New Labour

The NEC are considering whether to use STV for the CLP division of the NEC. This is important, and much discussion is to be had about whether and how this will change the power on the NEC and if its desirable. My helpful contribution is that we never use STV because our preferential systems are for single positions, maybe it would be good, particularly now that many CLPs send multiple delegates to Conference, but we are not talking about that yet.

Much more interesting are Charlie Mansell’s comments.


The results of the last NEC which were narrowly won by the right may underestimate their support.

Mind you, if we’re having STV for the CLPs we can have it for the ALC positions.

It all reinforces my feeling that the Left need, as a priority, to talk and listen to those who voted for Jeremy in 2016 and for Kier or Lisa in 2019. …