Opinion Polls: Heading Cameron’s Way, Slowly
I return to the subject of “iron laws” in politics in my column in The Independent on Sunday today. For all those who so enjoyed the Electoral Calculus chart, which I used, with permission, a while ago, here is an update.
This, the most complicated chart that is actually quite useful, plots the opinion-poll ratings of the two main parties (with the Lib Dems and Others as a residual) two years before each of the last seven elections, then one year before and then the election result.
It shows that public opinion tends to shift towards the Conservatives before elections when they are in government (the blue lines move to the right and down), and, less clearly, towards Labour when they are in government (the red lines move left, although not up, except before 2010).
The green line marks the shift in the opinion polls in the six months since May 2013, which was two years before the 2015 election. It is thus a quarter of the way towards its destination.
The average of the last eight polls from different companies is Conservatives 31.8 per cent, Labour 36.6 per cent, so the line has moved right and down. If it keeps going in a straight line, it will end in hung parliament territory, but the one thing that is really unlikely is a completely straight line.
So where will it end? We have three different forecasts.
1. Electoral Calculus’s own prediction, based on current opinion polls (right), is that there is a 91 per cent chance that Labour will be the largest party (81 per cent Labour majority plus 8 per cent Lab/LD coalition plus half of the 4 per cent “no overall control”).
2. Stephen Fisher of Trinity College, Oxford, as I say in my article, makes almost the opposite prediction, based on modelling opinion poll data from the past, like that in the Great Big Complicated Chart. He says there is an 88 per cent chance that the Tories will be the largest party.
As I commented on the blog last week, Fisher’s model does not account for the effect of UKIP winning a larger than 3 per cent share of the vote next time. I have been sceptical about the size of this effect, given that UKIP also takes votes from Labour, the Lib Dems and non-voters, and that it will be squeezed by the “A Vote for UKIP is a Vote for Ed Miliband” message, but it will surely reduce the Tory vote most.
3. The bookmakers, whose odds reflect the guesses people are prepared to back with money. The odds, Labour 4/6 to win most seats, Conservatives 11/8 and Lib Dems and UKIP 150/1, imply probabilities of 58 per cent, 41 per cent and 0.7 per cent respectively.
As I say in The Independent on Sunday, I think the Conservatives’ chances are better than that, but I defer to the greater wisdom of Molly Ivins, the Texas columnist, who said, according to my friend Matt Hoffman: “Anyone who would predict a presidential election one year out is a certifiable moron.”
Update: On the subject of iron laws of politics, or the contest of precedents, this by xkcd is very good (thanks to Omer Lev for reminding me of it).Tagged in: 2015 election, opinion polls
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