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.
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.