## Monday, February 6, 2023

### Math time

This is Joseph.

One of the great lessons of the Brexit referendum is that it makes sense to require a large majority to do a big change via a referendum. Why? Because change has costs and you might well end up with a policy that no longer has popular support:

Now look upon the rebuttal:

Notice the careful switching of the reference group. A large majority (70-75%) of the 52% of the voters to leave still have the same opinion. That is a large majority of half of the group. If we use the math suggested with his estimates we get:

52% x 0.725 + 48% x 0.05 = 40.1%

Which would suggest that the opposition to Brext, once the costs were known, is about 60-40 among the people who voted. Of course, young people (less pro-Brexit) have aged into voting in the past seven years and older adults (more pro-Brexit) have left us for a better place. A recent poll pegged the decision to leave as being correct as a view held by 34% of the population, which seems about right.

Now it is true that the vote was advisory, but there is a reason that a super-majority makes sense for this type of poll. A weak majority can easily drift back and it makes a country seem unreliable if major treaties can be snapped with a weak mandate. If the UK was utterly convinced that the EU was a bad plan (say 67% in favor of leaving) then it is also plausible that majority support would have survived the downside surprises.

Now this is a bit of an oversimplification, as the Brexit also had a misleading campaign. It promised to bolster the NHS, the British social medical care scheme, whereas it actually hurt it. People skeptical about claims were told they were part of Project Fear, a claim that the detractors were unduly pessimistic. Now it looks like they might have been correct and the planners of Brexit would have been well advised to consider that in terms of planning for how to keep public support high.

Now it is true that rejoining the EU is likely impossible, who wants a member who can leave with such a narrow majority of a single referendum, but it does suggest that there is also no plan to go forward from here. Brexit is done and will now be an never-ending series of pressure points. Lots of problems were very conveniently solved by Brexit: Spanish claims over Gibraltar and Northern Ireland both look a lot less pressing when the UK is in a free trade and movement compact with the other polity. Unification of Ireland, for example, brings many fewer obvious benefits when both parts are a part of the same large and democratic union.