Stephen Fisher and Rosalind Shorrocks
There is a lot of evidence from the academic research on forecasting that suggests it is a good idea to combine information from different sources (e.g. here). In US and German elections generating a forecast by combining the forecasts of others has a good track record. For the upcoming US presidential election pollyvote.org provides an average of different forecasts together with excellent summaries and discussions of the different methods and forecasts.
We have developed a similar method of combining forecasts for the UK’s referendum on EU membership on 23rd June 2016. The summaries of the average forecast win-probability and share of the vote for Remain by method and then overall are presented in the tables below. Note that there are different components for each because some of the source forecasts provide only probabilities or only vote share.
|Share of the vote||Remain||Leave|
|Combined forecast (mean)||53.6||46.4|
|Poll based models||54.0||46.0|
|Non-poll based models||52.0||48.0|
|Probability that Remain wins|
|Combined forecast (mean)||66.8|
|Poll based models||74.7|