David Leonhardt: The Brits and their maths

How a numbers problem helped create the Brexit mess. View in [Browser]( | Add nytdirect@nytimes.com to your address book. [The New York Times]( [The New York Times]( Tuesday, January 15, 2019 [NYTimes.com/David-Leonhardt »]( [Op-Ed Columnist] Op-Ed Columnist Most explanations of Brexit don’t involve a lot of math (or maths, [as the British say](. But I think math troubles — in particular, the difficulty people have in understanding probabilities — have played an important role in creating the mess that is Brexit. Let me explain. In 2013, Prime Minister David Cameron was looking ahead to a re-election campaign and trying to avoid losing too many voters to an anti-European Union political party. So he promised, if re-elected, to hold a referendum on whether Britain would stay in the union or not. He said that the referendum would have only two options — in or out — and that it would be binding. When Cameron made the promise, he and his advisers believed it to be “a relatively low-risk ploy to deal with a short-term political problem,” [as The Times later explained](. Virtually all political analysts believed that the referendum’s chances of passing were below 50 percent. And Cameron, along with much of Britain’s Conservative Party, [made a classic mistake]( of evaluating probabilities: They rounded down. They confused mere unlikelihood with virtual impossibility. They waved away the enormous damage that a yes vote would do by telling themselves, But it won’t happen. It did, of course. Now, Britain is left in a miserable situation. There is no good way for the country to remain in the European Union. Doing so would break the core promise of the referendum — that the result would be binding. But leaving the union imposes large burdens on Britain, in terms of higher living costs and lost jobs. The reason the country is having such a hard time deciding on the precise terms of Brexit is that there are no good terms. Brexit advocates campaigned by making outrageously unrealistic promises, and the country is now faced with the much less pleasant reality of what it means to divorce the European Union. All of this could have been avoided if the Cameron government had taken seriously the probability that the referendum would pass. 40 percent — or 20 percent or 10 percent or even three percent — is very different from zero percent when the consequences of the event in question are severe. Commentary from Europe British Parliament will vote today on Prime Minister Theresa May’s Brexit plan, which is less radical than many of her fellow conservatives want. The vote is widely expected to fail, but a close loss could empower her to seek slightly better terms from the European Union. A large loss could create yet more political turmoil. Here is a selection of commentary: “Defeat on Tuesday for her Brexit plan has been so thoroughly priced in,” writes [Robert Shrimsley of The Financial Times]( that members of Parliament “are almost blasé about what would be the most shattering rejection of any prime minister in modern times.” “At the moment,” [Jochen Bittner of Die Zeit writes in The New York Times,]( “it looks possible that all this will happen in the worst possible way, with no arrangement in place between Britain and the union on how to manage the separation.” [Polly Toynbee]( of The Guardian argues against the May compromise and for a second referendum. Regardless, she says, “There is no end in sight” to “a Brexit civil war that will last a generation.” The Economist also favors a second vote but has posted [a selection of op-eds on both sides](. [The Telegraph]( which favors a bolder version of Brexit, urges Parliament to “vote against it in large enough numbers to kill it dead, otherwise Theresa May will just keep bringing it back to the Commons until she gets her way.” ADVERTISEMENT If you enjoy this newsletter, forward it to friends! They can [sign up for themselves here]( — and they don’t need to be a Times subscriber. The newsletter is published every weekday, with help from my colleague Ian Prasad Philbrick. David’s Morning NYT Read [Theresa May, Britain’s Kafkaesque Prime Minister]( By TOM WHYMAN In her pointlessness, she can seem to form something like a coherent whole. The Full Opinion Report [Donald Trump: The Russia File]( By THE EDITORIAL BOARD Americans deserve to know what the president and Vladimir Putin are talking about. [Is 2019 Over Yet?]( By GAIL COLLINS AND BRET STEPHENS It’s been a very long two weeks. 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