Category Archives: Forecast updates

Final forecast from the Historical Referendums and Polls based method

by Stephen Fisher and Alan Renwick.

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.

That said not all the possible outcomes in this range are equally likely. Our forecast probability that Remain will win the referendum is 64 per cent.

The methods behind our forecast

Continue reading Final forecast from the Historical Referendums and Polls based method

Final combined EU Referendum forecast

by Stephen Fisher and Rosalind Shorrocks.

This forecast is based on data collected late on 22nd June. Yet again this method suggests Remain is most likely to win but there is a considerable chance that Leave may win. The probability that Remain will win is up from 62.3% on Sunday to 66.5% now. This reflects both better opinion polls in recent days and so polling models more favourable for Remain, and greater market confidence in a status quo victory.
The only component forecast that is less favourable to Remain is the citizen forecasts, and that is because we have restricted our sample to citizen forecasts over the last week. They are noticeably more equivocal.
The forecast share of the vote is once again little changed, with Remain predicted to get 53.3% and Leave 46.7% per cent of the vote.
Remain % share Leave % share Probability Remain wins
Betting markets 53.5 46.5 76.7
Prediction markets 73.4
Citizen forecasts  52.0  48.0 55.2
Expert forecasts 55.1 44.9  62.0
Volunteer forecasts 54.0 46.0 74.0
Polls 50.6 49.4 55.6
Poll based models 52.5 47.5 68.5
Non-poll based models 55.6 44.4
Combined forecast (mean) 53.3 46.7 66.5

(Individual forecasts collected on the evening of 22nd June 2016.)

There is another poll due during polling day but that would be unlikely to change our polling average. The markets may change, possibly dramatically during the day if people on the betting and prediction markets are following trends financial markets.

METHODOLOGY Continue reading Final combined EU Referendum forecast

Updated combined EU Referendum Forecast

by Stephen Fisher and Rosalind Shorrocks.

We offer our condolences to the family and friends of Jo Cox MP. We hope that it is not disrespectful of us to post this updated forecast now that the official campaigns have resumed.

Remain % share Leave % share Probability Remain wins
Betting markets 52.0 48.0 66.5
Prediction markets 65.6
Citizen forecasts  52.0  48.0 62.1
Expert forecasts 55.1 44.9  62.0
Volunteer forecasts 54.3 45.7 71.3
Polls 48.5 51.5 46.0
Poll based models 50.5 49.5 55.0
Non-poll based models 55.6 44.4
Combined forecast (mean) 52.6 47.4 62.3

(Individual forecasts collected on 18th June 2016.)

METHODOLOGY Continue reading Updated combined EU Referendum Forecast

Forecast update for the Historical Referendums and Polls based method

by Stephen Fisher and Alan Renwick.

We offer our condolences to the family and friends of Jo Cox MP. We hope that it is not disrespectful of us to post this updated forecast now that the official campaigns have resumed.

Our polling average now has Remain at 49% after setting aside Don’t Knows.

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

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

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

The methods behind our forecast

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 to BMG, ICM and ORB this week. The current average is based on the results of twelve polls from nine companies, of which six were conducted by phone and six online. All polls are adjusted to account for the tendency for phone polls to be more favourable to Remain. This is done by adding 1.75 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 a sharp drop in the probability of a Remain win to 60.6%, down from 67.7% last week. Similarly the forecast share of the vote for Remain has dropped from 53.8% to 52.7%. For the first time, our poll of polls of polls has Leave ahead, and more of the polls under consideration (see below for details) have had Leave ahead than have had Remain ahead. There has been little or no change in the expert forecasts and non-poll based models because of little or no new data. However there have been substantial changes in the betting and prediction markets, largely in response to the opinion polls. Intriguingly the volunteer forecasters at the Good Judgement Project now 72% chance to Remain, more than 10 points higher than the corresponding figure from the prediction markets: the biggest gap between these sources we’ve observed so far.

Remain % share Leave % share Probability Remain wins
Betting markets 51.5 48.5 60.7
Prediction markets 60.1
Citizen forecasts  52.0  48.0 64.4
Expert forecasts 55.1 44.9  62.0
Volunteer forecasts 54.2 45.8 72.2
Polls 49.6 50.4 45.7
Poll based models 51.0 49.0 59.0
Non-poll based models 55.6 44.4
Combined forecast (mean) 52.7 47.3 60.6

(Individual forecasts collected on 14th June 2016.)

METHODOLOGY Continue reading Updated combined EU Referendum forecast

A 50:50 forecast from the Historical Referendums and Polls based method

by Stephen Fisher and Alan Renwick.

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

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

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

The probability that Remain will win the referendum has fallen from 68% last week to just 51% this week. Continue reading A 50:50 forecast from the Historical Referendums and Polls based method

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