Polls, polls, lov-er-ly polls

One of the stories to come out of the 2015 General Election was how wrong the polling was in advance, and since then pollsters have been investigating how it went wrong:

“This week’s Polling Inquiry — what you need to know in advance” on the UK Polling Report site says:

“The major factor though looks likely to be sampling — pollsters interviewing people who are too easy to reach, too interested in politics and engaged with the political process and — consequently — getting the differential turnout between young and old wrong.”

John Rentoul argued convincingly in the Independent recently that “Opinion polls, like democracy, are the worst option… apart from all the others” and there has also been a BBC Radio 4 series starting to look at what happened, available on iPlayer “Can we trust the opinion polls?”

The problem with the 2015 polls is neatly summed up by this chart I made for a presentation just after the event. Expecting a close race, the narrative in the last couple of weeks was dominated by the question of who might do a deal with whom in order to reach Number 10, when we now know this wasn’t a remote possibility at all for Ed Miliband.

Whether different polling data in the run-up to the election would have changed the result seems, on the face of it, unlikely though.