Champions of the movement to withdraw the United Kingdom from the European Union, like champions of many causes and candidates, promised a range of positive results if the British would simply shed the burden of their participation in the Union. There would be billions of pounds available to improve public health, immigration would be sharply reduced and the economy would take off. Now, strangely, having secured victory, these champions are suggesting that what they promised will prove to be vastly greater than what they actually will deliver.
In fairness to all concerned, both champions and opponents were doing a lot of guessing. The European Union itself is a novel experiment in shared sovereignty. Every new challenge it faces, every new innovation it tries, represents a historic first. There are no controlled experiments, no epidemiological studies, no time-series analyses that provide even a modest degree of assurance about the results of any particular significant act affecting the membership and operation of the EU.
Which might make one cautious about promising too much, or predicting consequences too dire . . .