Why it's good that polls get reported so much

Welcome to the 137th edition of The Week in Polls (TWIP), which is a follow-up to last time’s piece on why banning polls would be a bad idea. This time it’s about why paying lots of attention to the polls is a good thing. While last week’s piece was based on firmly developed views, this time is a bit more speculative, drawing on recent academic articles that may yet be reinforced, or contradicted, by further work from the authors, their peers,¹ or indeed your own wise feedback to me.

Then it’s a summary of the latest national voting intention polls and a round-up of party leader ratings, followed by, for paid-for subscribers, 10 insights from the last week’s polling and analysis.

This week, that includes some striking similarities between Green and Reform voters.

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More stories about polling, please

I have a simple five step argument in favour of extensive coverage of political polling:

1. The polls are generally pretty accurate.

2. It is a good thing if accurate information is widely available.

3. But left to their own devices, people prefer spreading an inaccurate picture of polling.

4. Even worse, people tend to draw the wrong conclusions from small changes well within margins of error.

5. And therefore, we need lots of coverage of the polls, please, so that #3 and #4 do not drown out the good things.

Yes, once again I have an argument that the answer to problems with polls is more polling (coverage).²

Step one I’ve covered before (such as here) and last week’s edition was a plea for step two.

Step three is something anyone who follows polls on social media is likely to have noticed. People are much more likely to share a poll finding that contains good news for their favoured party or politician than one that doesn’t. Guilty.

There is more rigorous evidence to demonstrate this too:

Voters Share Polls That Say What They Want to Hear: Experimental Evidence From Spain and the USA by Alejandro Fernández-Roldán and Matthew Barnfield

We find no evidence of any effect of polling firms, fieldwork dates, or sample sizes on intentions to share polls. Above all, our results suggest that the main factor consistently affecting voters’ proclivity to share polls is the result of the poll itself.

A poll bringing you high quality findings doesn’t get it more shares. A poll bringing you what you want to hear does. Comfort polling trumps quality polling.

Now for step four which, on checking my references, turns out to be from one of the same academics. This time it is about how people perceive polls:

Momentum in the polls raises electoral expectations by Matthew Barnfield

Voters rely on opinion polls to help them predict who is going to win elections. But they are regularly exposed to different polling results over time. How do changes in the polls affect their expectations? I show that when the polls indicate that a party’s support has increased, voters’ expectations for that party’s performance will be higher than they would be at the same vote share but without such evidence of growth, because the party appears to have momentum… I find that this effect persists even when changes in vote share are well within the margin of error.

Add step three and four together and they suggest that, for example, a poll showing a mere one point rise in support for the Make All Letterboxes Vertical party³ will be disproportionately shared by supporters of vertical letterboxes compared to polls showing the party falling, and also that hearing of such a statistically insignificant move in the polls in favour of that party boosts perceptions of its campaign momentum.

You do not have to be a supporter of horizontal letterboxes to realise that is not good.

The antidote to all this? More and better polling coverage. More, so that the self-selecting bias of who shares what is swamped by the volume of coverage. And better, so that tiny shifts in the polls get drowned out in the noise of other data and in the rigour of better analysis.

(It is also why I include each week a table of all the polls in this newsletter and, in a related field, why I always blog every local council by-election result each week. Committing to cover them all is a deliberate move to help protect me against those temptations.)

Our media, I think it is fair to say, do rather better at the first - heavy coverage of polls - than of the second - with, as regular readers know, even respectable media outlets in the UK willing to call a one or two point change a ‘surge’.

But as ever, the issue there isn’t the polls. It’s what people choose to do with them.

More polling and more polling coverage, please.

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Voting intentions and leadership ratings

Here are the latest national general election voting intention polls, sorted by fieldwork dates:

Next, a summary of the the leadership ratings, sorted by name of pollster:

For more details, and updates as each new poll comes out, see my regularly updated tables here and follow The Week in Polls on Bluesky.

For the historic figures, including Parliamentary by-election polls, see PollBase.

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Last week’s edition

Why banning polls would be a bad idea

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What Green and Reform voters have in common, and other polling news

The following 10 findings from the most recent polls and analysis are for paying subscribers only, but you can sign up for a free trial to read them straight away.

1. A simple polling finding from More in Common about Reform and Green