The Metropolis

A smarter pollster says that a LibDem sweep would devastate Labour more than Conservatives

Darren Atwater | Monday 26 April, 2010 09:47

Nate Silver at FiveThirtyEight.com has taken a look at Labour incumbents after a LibDem sweep and it doesn’t look pretty for them.

Silver says that UK pollsters have been calculating their sums wrong:

[T]hey are based on the idea of a uniform national swing, i.e., that if Labour finishes 7 points below their standing from the previous election in 2005, their share of the vote will drop by 7 points in each individual district (better known as ‘constituencies’ in the U.K.).

I’ve designed an alternative approach which, while also based on fairly simple assumptions, is potentially more robust. The approach works by assigning shares of one party’s 2005 vote to another.

A 10% swing towards LibDem from Labour and Conservative could result in

Conservative	276	+78
Labour	218	-138
LibDems	123	+61
Others	15	+3
Northern Ireland	18	0

A 20% swing towards LibDem from Labour and Conservative could result in

Conservative	194	-4
Labour	154	-202
LibDems	272	+210
Others	12	0
Northern Ireland	18	0

In general, however, Labour backers should not take too much confidence from uniform swing calculations: they have been badly wrong in the past and there is some evidence that they may be badly wrong again. Particularly if Labour’s vote were to wind up in the mid-20s, its very hard to see how they could thread the needle in such a way that the outcome wouldn’t be devastating to them.

Read Silver’s argument here.

---