vendredi 24 juin 2016

Brexit: we should have known better


Well, Quebec voted no to leave Canada, Scotland, no to leave UK and then UK leaves the EU. It is a bit ironic when you see it from Quebec, although Europe is not a country per se.

So what happened?

I am not sure that pollsters failed that much. However, I think analysts -- and I include myself -- failed. And I know how and why I failed. At the beginning of the campaign, a colleague of mine, Henry Milner, told me that it may be that, in this referendum, the status quo side was the Leave side. His argument was that older people tended to vote Leave, that they were raised in a country that was outside the EU and they may want to go back to "normality".

So what is the consequence in terms of analysis? The "Law of even polls" -- which states that when it is equal, status quo or the more conservative side is likely to prevail -- still applies...but you ought to know which side is status quo! I should have known better. I amend my law, adding this by-law: If you want to know which side is status quo, look at how older people vote. They are the ones who win elections. People between 18 and 34 years old form less than 20% of the population and an even lower proportion of the voters.

So, here is the graph that I get when I attribute 67% of non-disclosers to the Leave side instead of the Remain side (the reverse of what I have done so far).  I get a perfect prediction of the results.

In conclusion

A number of analysts, journalists, pollsters noticed during the campaign that older people clearly favored the Leave side. This should have rung the bells and led us to conclude that, in a very close situation, the Leave side was likely to win. In my case, I should have listened and attributed two thirds of the non-disclosers to the Leave side instead of Remain. With this procedure, the prediction is perfect.

4 commentaires:

  1. Très intéressante comme toujours.
    Cela expliquerait - en bonne partie, il me semble - le résultat des deux référendums québécois... et de la défaite de 2014 du PQ.

    Paul Gagnon

  2. La différence avec le Brexit étant que le mouvement souverainiste s'est avéré être celui d'une génération plus que d’un classe d'âge. 40% en 1980, les personnes âgées votant pour le statut quo. 49% en 1995 alors que les boomers commencent à vieillir, remplaçant progressivement les disparus qui votaient non.

    Aujourd'hui, avec l'immigration, la jeunesse mondialisée et nombre de boomers désenchantés, la tendance est à la baisse, tranquillement (comme la révolution) mais surement!

    Paul Gagnon

  3. There's a bit of an ecological fallacy in the argument since older voters were less likely to be undecided in the polls. For your theory to hold, it would mean the reason why younger voters were undecided is because they were torn between voting with the age cohort or voting with their elders. I'm not sure that makes sense. It may be a combination of things, including undecideds who leaned Remain having a higher probability of not voting.

  4. See my posts "To Brexit or not to Brexit" and "Brexit, the day before" where I explain that I do not pretend that non-disclosers vote that way 67% for Leave (or Remain) but that non-proportional allocation allows for compensating a number of biases coming from the fact that older people in particular are less present in the samples, and when they are, less likely to reveal their preferences. I would also add that the older people who are in the samples may not be representative of their generation. So effectively, it may be a combination of things. It stays that, when I attribute 67% of non-disclosers to the Leave side -- as I did with success in many other instances -- I arrive at a perfect prediction.