The UK's Boris Johnson. Picture: REUTERS/TOBY MELVILLE
The UK's Boris Johnson. Picture: REUTERS/TOBY MELVILLE

As Britain’s negotiations to leave the EU enter their crunch moment, let’s be clear on one thing: the EU doesn’t need to punish Britain for leaving; the referendum did that just fine.

Latest figures show the warnings of economic self-harm Brexiters such as Boris Johnson derided as Project Fear are fast becoming real, while the promises of a Brexit dividend are still too remote even to assess.

Most studies seek to calculate the economic impact of the various degrees of Brexit. The UK treasury puts the damage at as much as 6% of GDP. Bloomberg Economics analyst Dan Hanson estimates that the level of UK GDP could drop between 3.2% and 6.7% by 2030, depending on the option chosen.

Such estimates are controversial. We don’t know the shape of the Brexit deal, including what arrangements will be put in place to keep trade flowing. And Brexiters complain that such exercises tend to use assumptions that favour negative results.

Yet it is possible to make some unbiased judgments about the costs of the vote itself to date. Doing so is useful as those unhappy with the prospects of a compromise Brexit deal advocate more extreme alternatives, such as leaving without one.

Post-Brexit economic models

In November 2017, four academics affiliated with the Center for Economic and Policy Research — led by German associate prof Benjamin Born — modeled how the UK economy would have grown had the referendum gone the other way. Their approach was to create a synthetic UK economy using the attributes of 30 Organisation for Economic Co-operation and Development (OECD) countries, including the US and Canada, whose GDP between 1995 and 2016 most matched that of Britain.

This month, they increased their estimate of the cost of Brexit to 2% of GDP, or about £35bn, from 1.3%. The researchers’ new output cost is £350m a week, the exact amount the Leave campaign claimed Brexit would save for use in the National Health Service.

Other attempts to measure the costs of the referendum all produce losses. A Financial Times average of several models back in June arrived at a Brexit cost of about 1.2% of GDP by the end of the first quarter of 2018.

Lower growth means lost income for the government, meaning it has to borrow more to meet its spending goals. Whitehall’s own analysis showed that 1% of lost GDP resulted in £11bn of extra borrowing. So Springford’s calculation of a gap of 2.5% would equate to £26bn of additional borrowing on a yearly basis, or £500m a week. 

Even with the model’s margin of error, it’s a striking result.

“If Britain had voted to Remain, our analysis suggests that the UK government deficit would largely have been eliminated by Brexit day” on March 29, Springford told me. “If Theresa May fails to land a deal by then, the costs to both the economy and the public finances will be even greater.”

If the UK remains in the customs union and achieves a trade deal with minimal barriers, tariffs or otherwise, the economy could recover lost ground in time. And for committed Brexiters, whose minds haven’t been changed in the intervening two years, the economic toll doesn’t matter. They voted for “control,” for sovereignty over laws and borders above all.

But those costs mean choices right now, as chancellor of the exchequer Philip Hammond works on a budget that must deliver on May’s promises to end austerity and help the worse off and somehow stick to fiscal prudence. They also limit the degree to which Labour leader Jeremy Corbyn can deliver on his sweeping pledges to nationalise industries and enlarge the welfare state. And they provide the closest thing we have to an arbiter of who was right during the campaign.