Final EU referendum forecast: Remain predicted to win 52-48

Posted on June 23, 2016 by The Constitution Unit

Stephen Fisher and Alan Renwick have developed a method for forecasting the outcome of the EU referendum based on current vote intention polling and analysis of opinion polling from previous referendums in the UK and across Europe. Their final forecast, taking account of polls published up to yesterday evening, suggests that Remain will win 52-48. However, there is a lot of uncertainty and a Leave victory can certainly not be ruled out.

The polls this week have been better for Remain than they were last week. Since this is our final forecast it makes sense for us to restrict our sample of polls to include in our polling average just the most recent poll from each company (or company-mode combination) over the last week. If we do this then our polling average finds Remain at 51 per cent after setting aside don’t knows. This is up two points from our polling average on Sunday. The two-point difference is partly due to restricting the sample from two weeks to just one, partly rounding error and partly to the fact that more of the polls than previously include Northern Ireland. So it is not clear whether the apparent movement towards Remain is real or not.

Our forecast share of the vote is 52 per cent for Remain, 48 per cent for Leave. This reflects an expectation of a 1.5-point rise in support for the status quo, based on the change that is visible on average between the final polls and the actual result in previous referendums in Britain or on the EU elsewhere. While this reflects the average historical experience we have explained here and here why the average may not be a very reliable guide.

The unreliability means there is a lot of uncertainty in our forecast. The 95 per cent prediction interval is considerably narrower than it was at the beginning of the week. But at ±10 points it is still very wide. So wide that Remain could reasonably be expected to get anywhere between 42 per cent and 62 per cent of the vote. Neither a comfortable Remain victory nor a comfortable Leave victory can be ruled out.

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EU referendum forecast update: probability of a Remain win now 52 per cent

Posted on June 19, 2016 by The Constitution Unit

Our polling average now has Remain at 49 per cent after setting aside don’t knows.

From this we forecast Remain to get 50 per cent of the vote.

The 95 per cent prediction interval is only a little narrower than ±12 points. So Remain are forecast to win between 39 per cent and 62 per cent of the vote.

The probability that Remain will win the referendum is now 52 per cent.

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EU referendum forecast update: probability of a Remain win slides to 51 per cent

Posted on June 14, 2016 by The Constitution Unit

Stephen Fisher and Alan Renwick have developed a method for forecasting the outcome of the EU referendum based on current vote intention polling and analysis of opinion polling from previous referendums in the UK and across Europe. This week the forecast has taken a dramatic turn with the probability of a Remain win falling from 68 per cent last week to just 51 per cent.

Our forecast has taken a dramatic turn. Last week our polling average had Remain at 51 per cent after setting aside don’t knows. It has this week dropped a further two points to 49 per cent. This means Leave is ahead in our polling average for the first time, with 51 per cent.

The forecast share of the vote for Remain has correspondingly dropped from 53 per cent to slightly over 50 per cent.

The 95 per cent prediction interval is still ±12 points. So we are now forecasting that both Leave and Remain will win between 38 per cent and 62 per cent of the vote.

The probability that Remain will win the referendum has fallen from 68 per cent last week to just 51 per cent this week.

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EU referendum forecast update: probability of Remain win falls for second consecutive week

Posted on June 9, 2016 by The Constitution Unit

Stephen Fisher and Alan Renwick have developed a method for forecasting the outcome of the EU referendum based on current vote intention polling and analysis of opinion polling from previous referendums in the UK and across Europe. For the second consecutive week the probability of a Remain win has fallen and now stands at 68 per cent.

Remain have continued their gentle slide in the polls. Last week our polling average saw Remain drop from 53 per cent to 52 per cent. Now they are on 51 per cent after setting aside don’t knows.

The further one-point drop in our polling average has produced a one-point drop in the forecast share of the vote for Remain, from 54 per cent to 53 per cent.

The 95 per cent prediction interval is still ±12 points. We are now forecasting that Remain will win between 40 per cent and 65 per cent of the vote.

The probability that Remain will win the referendum is now down to 68 per cent.

The method behind this forecast is based on the historical experience of referendum polls and referendum outcomes in the UK and on the EU elsewhere, as discussed here.

Our polling average is constructed by taking the most recent poll from each company within the last two weeks. If a company uses both phone and online modes then both the most recent phone poll and most recent online poll are used. This applies just to ICM this week. The current average is based on the results of eight polls from seven companies, of which three were conducted by phone and five online. All polls are adjusted to account for the tendency for phone polls to be more favourable to Remain. This is done by adding 2.2 to the Remain share for online polls and subtracting the same amount for phone polls.

This post was originally published on Elections Etc. and is re-posted with permission.

About the authors

Dr Stephen Fisher is an Associate Professor in Political Sociology and the Fellow and Tutor in Politics at Trinity College, Oxford.

Dr Alan Renwick is the Deputy Director of the Constitution Unit.

EU referendum forecast update: probability of Remain winning falls to 73 per cent

Posted on June 2, 2016 by The Constitution Unit

Stephen Fisher and Alan Renwick have developed a method for forecasting the outcome of the EU referendum based on current vote intention polling and analysis of opinion polling from previous referendums in the UK and across Europe. Since last week’s update the probability of a Remain win has reduced from 79 per cent to 73 per cent.

The small shift towards Remain in the polls that we observed last week has been reversed. Setting aside don’t knows, our polling average for Remain has dropped back from 53 per cent to 52 per cent. Despite there being little difference between the headline figures for yesterday’s ICM phone and online polls, our estimate (and corresponding adjustment) for the typical difference between the two modes of interviewing has barely changed.

The one-point drop in our polling average has led to a corresponding one-point drop in the forecast share of the vote for Remain, from 55 per cent to 54 per cent. The 95 per cent prediction interval surrounding this estimate has again narrowed very slightly to ±12 points. So we are now forecasting that Remain will win between 42 per cent and 66 per cent of the vote.

Overall the probability that the Remain vote will be larger than the Leave vote has dropped from 79 per cent last week to 73 per cent now.

The method behind this forecast is based on the historical experience of referendum polls and referendum outcomes in the UK and on the EU elsewhere, as discussed here.

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