Will this still stand when the results are known?
With YouGov yesterday showing a Labour share of 28% while ComRes for the Indy this morning puts it at 24% I thought it might be useful to remind ourselves of the “PB Golden Rule of Polling”. This is based on the the polling record at every single major election since the 1980s where the survey with Labour in the least favourable position has been the best indicator of voting intention.
There is no science to this – it just happens to have been what has happened. This is the record which I have rehearsed here before and only includes elections where more than one pollster has carried out surveys.
June 2009: Euro Election Four pollster did surveys and the worst share predicted for Labour was 16%. The party got a smaller share than even that.
July 2008: Glasgow East by-election Two polls showing Labour leads of 14% and 17%. Labour lost.
May 2008: Crewe & Nantwich by election Two pollsters did surveys showing that Labour would lose – but in each case the margin predicted was smaller than the outcome.
May 2008: London Mayoral Election. Four pollsters carried out surveys and three suggested that it was neck and neck between Labour’s Ken and Boris. The fourth had Boris ahead by what turned out to be the precise margin of victory.
May 2005: general election. All the pollsters’ final polls bar one had Labour with a bigger vote lead than was actually achieved. The one exception, NOP for the Independent, got it precisely right and then got dropped by the paper.
June 2004: London Mayoral race. Two pollsters did surveys – the one with Labour in the least favourable position got it almost precisely right.
June 2004: Euro elections. Two firms did polls both of them overstating Labour’s eventual position.
June 2001: general election. Labour won with a 9.3% lead on votes. None of the pollsters had this in single figures and one campaign poll had the party 30% ahead.
May 1997: general election. Labour won with a 14% lead on votes. The best pollster was ICM who had Labour in the least favourable position although their final poll did understate Tony Blair’s party.
April 1992: general election. The closest final poll had the Tories ahead by just 0.5%. John Major’s party won with a lead on votes of just under 8%.
The pollsters have got a lot better in refining their approaches to deal with Labour over-stating and ahead of the June 4th 2009 Euro elections I was suggesting that the “rule” might not survive. It did but I’m not so confident about how it will operate at the coming general election. Could the mechanisms that have been introduced to deal with Labour over-statement have gone too far?
What is looking likely is that the outcome will be unprecedented and many of the assumptions that we make will probably have to be re-thought.