‘Unionists Unite! You have Nothing to Lose but your…Split Vote’

A further ‘argument’ for having an indy list party is that the unionists have a ‘massive inbuilt advantage’ in the Additional Member System (AMS) used for the Scottish Parliamentary elections, because there are three unionist parties (Tories, Labour and Lib Dems) and the indy side has ‘only’ two (SNP and Greens).

Therefore, they claim, it only stands to reason that the indy side should also have three parties too.

In an ‘electoral arms race’, the uncritical thinking is that what they have, we should have too, because there are three of them and they can thus attain many more seats than they would ever be able to get than if there were only two or even one of them. Right?

Even a cursory familiarity with the d’Hondt algorithm informs us that in each round, the party with the highest number of votes wins that seat. One might surmise, then, that the more a party’s vote is split, the more its chances of winning list seats are hampered.

The only way to find out where the truth lies is, as ever, by modelling the various scenarios.

We looked at exactly this back in July, where all the various permutations were modelled using seat projections from the latest Panelbase poll:

  • Lib Dem vote goes to LAB
  • Lib Dem vote goes to CON
  • CON takes LAB vote, plus Lib Dems
  • LAB takes CON vote, plus Lib Dems
  • CON takes LAB and Lib Dem vote
  • LAB takes CON and Lib Dem vote

Obviously, these are all utterly absurd scenarios, but they need to be modelled just to deal with the misinformation spread on social media about this issue. Assertions have been made about how the list algorithm works, which can be readily tested: thus the only way to answer this factoid once and for all is to conduct some data analysis.

Here again is the baseline prediction. The SNP and Greens together have 14 seats, and the three unionist parties have 42. That’s our starting position.

CON with LAB (LAB takes all LD vote)

The unionist bloc is two seats up.

LAB with CON (CON takes all LD vote)

The unionist bloc is three seats up.

CON with LD (CON takes all LAB vote)

The unionist bloc is two seats up.

LAB with LD (LAB takes all CON vote)

The unionist bloc is three seats up.

Let’s go all in and see what the ‘black box’ of AMS would spit out if there was only one unionist party now.

CON takes LAB and LD vote

The unionist bloc is four seats up.

LAB takes CON vote and LD vote

The unionist bloc is five seats up.

In every possible permutation of the unionist vote, they are seen to gain seats (albeit marginally) by combining their vote.

In other words, Unionism actually suffers from their split across three parties, getting fewer seats than if there was only one or two unionist parties.

So you can see, the assertion that Unionist parties ‘massively benefit’ from their ‘split vote’ is yet another utterly baseless factoid presented as “common sense” within the independence community.

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