Which votes get transferred with the Single Transferable Vote?

Dylan Difford, guest contributor. Opinions and research are solely the author's and do not necessarily reflect the opinions of the ERS.

Posted on the 17th August 2021

The Electoral Reform Society has long found the Single Transferable Vote (STV) to be the best option for electoral reform. The ERS still promotes STV to this day, although there have been a few tweaks to the original idea over the last century.

With STV, each constituency elects a small group of MPs and voters rank candidates according to their preferences. To work out who gets elected, you first need to work out the quota. Candidates that exceed the quota are elected, with any surplus votes (total votes minus the quota) transferred to each voter’s next choice as indicated on the ballot paper.

Once any candidates who beat the quota are elected, there is another round of counting to see if any other candidates have reached the quota now surplus votes have been transferred. If no candidate meets the quota in a particular round of counting, the candidate with the least votes is eliminated and their votes are redistributed to their voters’ next extant preference. This continues until all the seats have been filled. Counting can be done by hand or, to speed things up, by using scanning machines.

But how do you work out which votes for a winning candidate count as the surplus and should be transferred? Well, there are two main methods – the ‘Hare’ or random method and the ‘Gregory’ or fractional method. To avoid confusion with the Hare quota, we’ll go by the descriptive names.

Random Selection

The random method – which is used for most elections in Ireland – involves the surplus being taken from a random selection of ballots. How the randomness is achieved varies from implementation to implementation – taking them from the last bundle or every nth vote being common – but they should all ideally achieve a similar result.

If 1,000 votes have been cast for a winning candidate on a quota of 750, you would randomly select 250 votes to be transferred to their voters’ next preference.

Fractional Transfers

The fractional method – used for all STV elections in Scotland and Northern Ireland and elections to the Australian and Irish Senates – involves all votes for a winning candidate being transferred, but at a fractional value.

If 1,000 votes have been cast for a winning candidate on a quota of 750, rather than transfer a quarter of the votes at full value, you transfer all of the votes at value of 0.25. These fractions of votes will then be transferred to their voters’ next preference and will hold this value until they are used up or become part of another surplus and are split into smaller fractions.

Upside and Downsides

The main advantage of the random method is that it is significantly easier and quicker if you are counting by hand. But, as with anything random, it is subject to risks of unrepresentativeness. It could be that your randomly selected group of candidate A’s voters is skewed in favour of candidate B, even though most candidate A voters preferred candidate C. In a narrow race, this skew could make all the difference.

Under the fractional method, this wouldn’t happen as every candidate A voter would get to see their surplus go to their next choice, just at a fractional value. With enough elastic bands and post-it notes to record the strength of each bundle of votes, you can do this by hand – but electronic counting machines can make the process just as fast as the random method.

Of course, the relative downsides of the random method are nothing like the repeated failures of the current First Past the Post system. While STV has constantly been improved over the years, Westminster’s inflexible First Past the Post system has languished, doomed to making the same mistakes over and over again, failing to properly represent British voters.

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