Thursday, March 16, 2023

SNP use STV

Since I'm no longer in Scotland, I haven't followed the SNP leadership contest too closely, but this recent article caught my eye. It's mostly about membership numbers and transparency, but the bit I found most interesting was mention - at the very end - that the process uses the single transferable vote system.

This is slightly unusual terminology, since STV is normally used to refer to PR systems. When only one person is being elected, this is usually referred to as the alternative vote system - something I blogged about long ago

Nonetheless, it could be a useful example next time I'm teaching about these voting systems. I've previously used Conservative leadership contests as an example, though these aren't ideal in a couple of respects. First, unless there's a 'coronation' without a vote (as happened for May and Sunak), the final vote goes to party members, rather than MPs. This changes the electorate between rounds. Second, as a sort of consequence of this, someone can get over 50% in earlier rounds but not automatically win. This happened in 2019, when Boris Johnson received over 50% in the fourth and fifth rounds.

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