Are public purse voters the bedrock of Labour support?
Last July Ipsos-MORI introduced a novel new weighting to try to deal with the over-representation of Labour supporters in polling samples. Unlike the other polling firms who weight by past vote or past party ID MORI now split their samples into those who are on the public pay-roll and those who are not.
Just look at the chart above to see two key elements. Conventional telephone polling seems to reach many more public sector workers than their numbers in the adult population suggest and in each poll since the change MORI has to scale their influence back quite considerably. In almost every monthly survey the public sector respondees have been well over double what they should be and the numbers adjusted accordingly.
And this is having an impact on the overall poll findings. The headline shares from those who are 100% certain to vote had the Tories 20 points ahead on 48%. Yet amongst the public sector workers polled Labour was in the lead. And If the “payroll” vote had been excluded then the Tory share would have been 50% with Labour down at 27%.
Quite why public sector workers figure so prominently in polls is had to say – but it happens month after month and I’m sure that the other phone pollster have the same experience. They just deal with the distortion in a different way.