How good is YouGov?

The question of whether internet polling is better or worse than face-to-face or telephone polling quite often causes sparks (friendly of course) to fly between different pollsters and pundits. So I thought it would be useful to compare YouGov against all the other political pollsters (except for BPIX – because they also use the internet but also aren’t a member of the British Polling Council and so are of questionable reputation*).

Here are the monthly average scores since the general election for the three main parties; the solid line is the average of all the polls with fieldwork dates in that month by firms other than YouGov; the dotted line is the average of the YouGov polls from that month.

The conclusion? YouGov gives Labour and the Conservatives regularly roughly the same ratings as other pollsters – sometimes a little higher, sometimes a little lower.

But their Liberal Democrat ratings are consistently lower than other pollsters. Why and who is right? Debate away…

* Rather strangely, the people behind BPIX do seem credible and knowledgeable. But they don’t seem very open about how BPIX operates. Their website, bpix.co.uk, has been “under construction” for as long as I can remember, they aren’t a member of the British Polling Council and my previous email query to them didn’t solicit a reply – though of course emails do sometimes go astray. If anyone from BPIX is reading this please do use the comments facility to clarify these matters.

UPDATE: I returned to the question of YouGov’s reliability in 2022 and here is a piece from 2023 on the reliability of online panels more generally.