Tweeting uniform national swing

A tweet arrives:

@NickAnstead Just found an excellent way to break British constitution: Enter: LD – 33, Cons – 31, Lab – 29 = MELTDOWN

The link takes you the UK Polling Report swingometer, and if you put in those polling figures it makes an estimate of how many seats in Parliament that would net you at a General Election, assuming that there was uniform national swing – a highly dodgy statistical notion that means there is no individual campaigning in individual constituencies, and that every voter in the country behaves exactly like the 1,000 or so people who were polled in the first place.

Anyway, key in those polling figures and you get the following seat distribution:

Party Poll % No seats
Tory 31 213 (+15)
Lab 29 281 (-75)
Lib Dems 33 125 (+63)
Others 7 13 (+1)
Northern Ireland 18 (nc)

Hung Parliament, Labour 45 seats short

Now those polling figures are unlikely, but not impossible. Labour’s numbers are about right, but we’d have to gain 11 points over our most optimistic recent polling, and it would have to be at the Tory’s expense. (Well all we need is a few more voters like the ones in Brighton…)

But the scariest thing in those numbers is the repeated reflection of just how unfair the voting system is, and what an uphill battle it is for the Liberal Democrats.

It’s not as if pushing the Labour party into third place is completely impossible. We did it at the last local elections, and now some (well, one) serious political commentators are suggesting it might even happen in the next general. The excellent Stephen Tall looks into that here.

But if the Lib Dems were to actually beat the Labour party into third place in terms of popular vote, if we were to beat them by four percent, we still be hundreds of seats behind them. The Labour party on 29% get more than double the number of seats the Lib Dems get on 33%.

The starkest illustration of that is to put into the swingometer 32% for each of the parties. On exactly the same percentage vote, the Lib Dems get 106 seats, the Tories 208 and the Labour party a massive 305, 21 short of a majority. There’s some information on that in the UK Polling Report’s “Electoral Bias” page, but itself with a bias in favour of the big two parties. There’s something in the tone of the writing that suggests the Lib Dems are only there to help one or prevent the other large party from forming a majority.

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