Combined EU Referendum forecast update

Stephen Fisher and Rosalind Shorrocks.

This week’s forecast shows another drop in the probability of a Remain win, this time to 67.7%. Part of the reason for the drop is the introduction of significant new data sources and methodological changes (detailed below). But it is also true that all of the component methods, including those without methodological changes, have seen drops in the probability of a Remain vote. By contrast the forecast share of the vote for Remain continues to hover around 54% as in previous forecasts.

Remain % share Leave % share Probability Remain wins
Betting markets 53.2 46.8 72
Prediction markets 70.6
Citizen forecasts 64.3
Expert forecasts 55.1 44.9  62.0
Volunteer forecasts 54.2 45.8 74.2
Polls 51.1 48.9 59.1
Poll based models 53.5 46.5 72
Non-poll based models 55.6 44.4
Combined forecast (mean) 53.8 46.2 67.7

(Individual forecasts collected on 8th June 2016.)

METHODOLOGY Continue reading Combined EU Referendum forecast update

Historical Referendums and Polls based Forecast Update

by Stephen Fisher and Alan Renwick.

Remain have continued their gentle slide in the polls. Last week our polling average saw Remain drop from 53% to 52%. Now they are on 51% 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% to 53%.

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

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

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.

Updated combined EU Referendum forecast

Stephen Fisher and Rosalind Shorrocks.

This week’s forecast shows the probability of a Remain win reduced to 71.9%, down from 76.1% last week. Once again the forecast share of the vote for Remain, at 53.7%, is similar to all our previous combined forecasts.

Remain % share Leave % share Probability Remain wins
Betting markets 54.1 45.9 73.7
Prediction markets 73.8
Citizen forecasts 68.4
Expert forecasts 56.0 44.0
Volunteer forecasts 54.3 45.7 76.1
Polls 51.4 48.6 63.6
Poll based models 54.5 45.5 76.0
Non-poll based models 51.8 48.2
Combined forecast (mean) 53.7 46.3 71.9

(Individual forecasts collected in the morning of 1st June 2016.) Continue reading Updated combined EU Referendum forecast

Forecast update for the Historical Referendums and Polls based Method

by Stephen Fisher and Alan Renwick.

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% to 52%. 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% to 54%. The 95% prediction interval surrounding this estimate has again narrowed very slightly to ±12 points. So we are now forecasting that Remain will win between 42% and 66% of the vote.

Overall the probability that the Remain vote will be larger than the Leave vote has dropped from 79% last week to 73% now. Continue reading Forecast update for the Historical Referendums and Polls based Method