EU referendum forecast update: 79 per cent chance of Remain winning

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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 the last update two weeks ago the probability of a Remain win has increased from 72 per cent to 79 per cent.

There has been a small shift towards Remain in the polls over the last two weeks. Excluding don’t knows, our polling average for Remain has moved from 52 per cent on 10th May to 53 per cent now. This figure is based on the most recent polls from each of seven companies: one from each but two from ICM (one by phone and one conducted online). The Remain share has been adjusted down by 2.15 points for telephone polls and up by the same amount for online polls to account for the relatively stable gap between these different methods in the levels of support they tend to give the two sides.

Using the historical experience of referendum polls and referendum outcomes in the UK and on the EU elsewhere, as discussed here, our latest forecast is for Remain to win 55 per cent of the vote in a month’s time. The 95 per cent prediction interval surrounding this estimate has narrowed very slightly to ±12.5 points. So we are forecasting that Remain will win between 43 per cent and 68 per cent of the vote.

Values closer to the middle of this range are more likely. Overall the probability that the Remain vote will be larger than the Leave vote is now 79 per cent, up from 72 per cent two weeks ago.

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: little change from last month

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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 around the world. This month’s forecast is little different from that published last month, continuing to show Remain on 54 per cent and Leave on 46 per cent.

We have published two previous forecasts of the result of the UK’s referendum on EU membership, which are based on current vote intention opinion polls for this referendum and on the historical experience of referendum polls and referendum outcomes in the UK and on the EU elsewhere. The main ideas behind this approach are set out here. This post offers an update.

There is little change in our forecast since this time last month. After allowing for some difference between telephone and online polls, the relative levels of support for Leave and Remain have been remarkably steady. The online polls are much more common than telephone polls and they have been suggesting the race is neck and neck. The telephone polls are still showing greater levels of support for Remain than online polls. Our estimate of the current gap between the polls from these two modes is not much diminished from last month. After excluding don’t knows, telephone polls tend to put Remain 4.5 points higher than do online polls. Adjusting Remain up by half this amount in online polls, and correspondingly down in telephone polls, leads to a current polling average of 52 per cent Remain, 48 per cent Leave.

Although this is the same as last month after rounding, the underlying estimate is slightly more favourable for Remain. However, because we are closer to referendum day we are also projecting a smaller rise between now and 23rd June in support for Remain in the polls. These changes roughly cancel out and so our forecast for the referendum outcome is still 54 per cent Remain and 46 per cent Leave. Again this is the same as last month after rounding.

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Second forecast for the EU referendum

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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 around the world. Last month, in their initial forecast, they suggested that Remain had an 87 per cent chance of winning. In this second forecast this has now dropped to 73 per cent. 

A month ago we issued our first forecast for the EU membership referendum on 23 June . Based on an analysis of referendums in the UK and on the EU outside the UK, and on vote intention opinion polls we forecast that Remain had an 87 per cent chance of winning, and that Remain would get 58 per cent of the vote, plus or minus 14. This was in part based on our polling average (excluding don’t knows) of 55 per cent for Remain on 11 March.

Our current forecast suggests that the contest is a fair bit closer. Our polling average now puts Remain on 52 per cent. We now give Remain a 73 per cent chance of winning and estimate that the Remain share of the vote will be 54 per cent, plus or minus 13 points.

The key change here is the drop from 55 per cent to 52 per cent for Remain in the polling average. The main reasons for this are as much or more methodological than substantive.

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