Business Management

Data expert: Brexit referendum is on a razor's edge

The following is an edited version of a blog written by Partha Sen, CEO of data analytics firm Fuzzy Logix for his personal site. It follows this earlier view. For another point of view on the Brexit vote that is based on social media sentiment, data visualisation firm Tableau has been maintaining this tracker.


In London this week on business, I can feel the anticipation and nervousness in the air for the outcome of Thursday’s EU Referendum. The news channels are now providing round-the-clock analysis and news coverage and, walking around London, ‘Referendum’ is definitely the word on the street.

Well, as far as the polls for Brexit are concerned, there has been some significant shift in momentum. It appears that, since the beginning of June, the ‘Leave’ campaign has gathered steam and is now ahead of ‘Remain’ by a margin of about 2.5% (see Chart A). 


Chart A: Trends in Brexit Polls Based on Trailing 2 Week Averages from Various Polls

Since the beginning of the month, 25 polls have been published by various pollsters. The averages of these polls show a very interesting phenomenon. The majority of pollsters reported that the ‘Leave’ campaign is ahead, with some of them reporting it to be ahead by a margin of 5% or more (see Chart B).

In contrast, the pollsters who are reporting the ‘Remain’ campaign to be ahead are reporting a much smaller lead of 1% or less. Based on these margins from various pollsters, prima facie it appears that the ‘Leave’ campaign has gathered momentum beyond statistical margins of error.


Chart B: How the Pollsters have reported since June 1st?

However, by dissecting the data further, we come to a slightly different conclusion. I analysed the Brexit polls for two different date ranges:

-      June 1st-14th

-      June 15th onwards

I did this for obvious reasons. From June 15th onwards, the ‘Remain’ campaign seemed to have clawed back and regained some of its losses. Also, it is perceived that the tragic shooting of Jo Cox MP, on June 16th, has had a negative impact on the ‘Leave’ campaign. Between June 1st and June 15th, the ‘Leave’ campaign, on average, polled 46.1% versus 43.9% for the ‘Stay’ campaign. That’s the widest lead the Brexit campaign has ever had since January of this year (see Chart C).

Another indicator of momentum being gained by the ‘Leave’ campaign is that, out of 15 polls during this time period, 10 of them reported ‘Leave’ to be ahead, sometimes by significant margin. 


Chart C: Trends from Polls June 1st-June14th and June 15th onwards

From June 15th onwards, though, the data shows that momentum has shifted back in favour of a ‘Remain’ vote. Of the 10 polls conducted since June 15th, 6 are reporting the ‘Remain’ to be ahead. The average from these polls show a statistical dead heat with ‘Remain’ at 44.4% and ‘Leave’ polling 44.6%. Also, the minimum and maximum vote share for both camps from these polls is very similar, which is another indicator of how tight this referendum has now become. 

Chart D, below, shows the changing margins for ‘Remain’ or ‘Leave’ throughout 2016 to date.  The current ‘Leave’ victory margin is wider than the initial ‘Remain’ margin in January of this year. 

Chart D: Averages from polls that reported 'Stay in EU' to be ahead versus those that reported 'Leave EU' to be ahead

In the end, it is my belief that the outcome will be decided by two factors: the percentage of voters who feel that the UK should leave the EU but don’t have the conviction to overturn the status quo and secondly, the undecided voters. The proportion of undecided voters has steadily come down and stands at about 10% now (see Chart E). The way these late decision makers vote could be the key.


Chart E: Proportion of undecided voters

In conclusion, the referendum is tight and the outcome could be decided by less than 250,000 votes and, in the extreme case, maybe even less than 100,000 votes. However, ‘Remain’ could win by a wider margin if a percentage of ‘Leave’ supporters don’t ultimately have the conviction to vote against the status quo and eventually decide not to vote or vote to stay. It will be interesting to watch the results on June 23rd. I would have loved to watch the outcome from one of the many popular bars in London. I will, however, be following the results with interest!  


Also read:

What social media tells us about Brexit

Brexit vote fever has been heated by social media

Data expert sees narrow Remain vote


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