With conference season over, we’re beginning to get the first indications of how the annual party gatherings affected voting intention. Much has been said and written, but what did the public actually make of it all?
The three polls we have so far, with changes compared with the same pollster’s last poll before 15th September, are:
BMG: Con 38 (+1) Lab 39 (+1) LD 10 (-1) UKIP 4 (-3)
Opinium: Con 39 (=) Lab 39 (+1) LD 7 (=) UKIP 6 (=)
YouGov: Con 41 (+1) Lab 37 (+1) LD 9 (-2) UKIP 4 (=)
Looking at the changes, the most noticeable thing is how little movement there is in the main party vote shares, with both Labour and the Tories both being indicated within a point of where they started in all three polls.
In fact the only thing that even approaches a pattern in these numbers is that Labour and the Tories between them seem to have gained slightly at the expense of the Lib Dems and UKIP, though the main parties are still several points below the 84.5 per cent of the Great Britain vote they collectively polled at the general election.
These figures represent a statistically insignificant swing of less than 0.2 per cent from Conservative to Labour over the conference season.
This is not the impression you might have got from the much retweeted polls conducted during conference season, a couple of which showed sharp swings in opposite directions, each of which was subsequently reversed. This was readily foreseeable, because as well as random error, polls are also subject to non-random error such as response bias, where one party’s supporters are differentially likely to participate in a poll, and which can be unstable around events such as conferences.
To get an idea of how much public opinion actually changes, we need to smooth through both types of volatility by taking an average of polls. There are different ways of doing this, but when looking at month-to-month changes, they tend to give similar results.