A question about swings

[Geoffrey Howe]

I have seen - or so I think - conflicting methods of calculating swings.

In America, it seems to be difference between two candidates at election 1, plus the difference at election 2. So 56.7/43.3 --> 55.2/44.8 is a 3 point swing.

In the UK, it seems to be half of this. So the above is a 1.5 point swing.

Are my observations correct?

[Torie]

I have seen - or so I think - conflicting methods of calculating swings.

In America, it seems to be difference between two candidates at election 1, plus the difference at election 2. So 56.7/43.3 --> 55.2/44.8 is a 3 point swing.

In the UK, it seems to be half of this. So the above is a 1.5 point swing.

Are my observations correct?

Yes in general, although the PVI calculation that is popular now due to the Cook Report, measuring the difference between the national POTUS percentages as compared to a given local constituency, does use the divide by 2 formula, so if Trump broke even with Biden in a CD, the PVI would be 2.25% R (the Trump losing margin of 4.5%/2). Personally I prefer the divide by 2 approach myself.

[Geoffrey Howe]

I have seen - or so I think - conflicting methods of calculating swings.

In America, it seems to be difference between two candidates at election 1, plus the difference at election 2. So 56.7/43.3 --> 55.2/44.8 is a 3 point swing.

In the UK, it seems to be half of this. So the above is a 1.5 point swing.

Are my observations correct?

Yes in general, although the PVI calculation that is popular now due to the Cook Report, measuring the difference between the national POTUS percentages as compared to a given local constituency, does use the divide by 2 formula, so if Trump broke even with Biden in a CD, the PVI would be 2.25% R (the Trump losing margin of 4.5%/2). Personally I prefer the divide by 2 approach myself.

Makes sense. I prefer the division method too; 56.7--> 55.2 doesn't 'feel' like a 3 point swing.

[Storr]

I have seen - or so I think - conflicting methods of calculating swings.

In America, it seems to be difference between two candidates at election 1, plus the difference at election 2. So 56.7/43.3 --> 55.2/44.8 is a 3 point swing.

In the UK, it seems to be half of this. So the above is a 1.5 point swing.

Are my observations correct?

Yes in general, although the PVI calculation that is popular now due to the Cook Report, measuring the difference between the national POTUS percentages as compared to a given local constituency, does use the divide by 2 formula, so if Trump broke even with Biden in a CD, the PVI would be 2.25% R (the Trump losing margin of 4.5%/2). Personally I prefer the divide by 2 approach myself.

Makes sense. I prefer the division method too; 56.7--> 55.2 doesn't 'feel' like a 3 point swing.

This is total conjecture on my part, but I could imagine the American method of calculating swings being first used in the media (or by winning campaigns) because it sounds more impressive and attention grabbing to have an election with a 3 point swing instead of a 1.5 point swing. Then over time that way of calculating swings became the standard in the country.

[Geoffrey Howe]

I have seen - or so I think - conflicting methods of calculating swings.

In America, it seems to be difference between two candidates at election 1, plus the difference at election 2. So 56.7/43.3 --> 55.2/44.8 is a 3 point swing.

In the UK, it seems to be half of this. So the above is a 1.5 point swing.

Are my observations correct?

Yes in general, although the PVI calculation that is popular now due to the Cook Report, measuring the difference between the national POTUS percentages as compared to a given local constituency, does use the divide by 2 formula, so if Trump broke even with Biden in a CD, the PVI would be 2.25% R (the Trump losing margin of 4.5%/2). Personally I prefer the divide by 2 approach myself.

Makes sense. I prefer the division method too; 56.7--> 55.2 doesn't 'feel' like a 3 point swing.

This is total conjecture on my part, but I could imagine the American method of calculating swings being first used in the media because it sounds more impressive and attention grabbing to have an election with a 3 point swing instead of a 1.5 point swing. Then over time that way of calculating swings became the standard in the country.

Haha, yes.