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.
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.