by Rob Marchant
Ah, the panic. You can see it setting in as there is a blip downwards in the polls. Two consecutive polls show Labour and the Tories neck and neck, and we have a letter to the Guardian. As Uncut’s Atul Hatwal noted last week, there are now rumblings on the Labour right.
But while it is a perfectly respectable aim to ask Miliband to change course on a raft of policy areas, one cannot help but think it is a conversation we should have been having two or three years ago.
The good news is that this jitteriness is based on very little change in the actual prognosis.
To explain: political journalists are not, in the main, statisticians. Neither are politicians. And so both groups often subscribe to a mathematical fallacy, and it’s this: the polling of today is our best indicator of a general election result in X years time. It’s not. It’s a very rough guide which fails to account for the cycle of the parliamentary term, and in particular an opposition’s mid-term bounce. For the hard of maths, you can skip the next nerdy paragraph and trust us on this.
Our best guess – the expected value – of a general election vote-share lead is not equal to the value of our polling lead now. It’s equal to the value of our polling lead plus our expectation of how much that lead is going to change in between now and then. Trouble is, that second bit is crucial and historically, it’s not zero. In short, it is reasonable to argue that we shouldn’t just extrapolate today’s poll out to 2015 in a straight horizontal line. For an opposition party, it should be a line that inclines downwards.








