Goldman Sachs reckons sterling could depreciate by 15-20 per cent if the UK votes to leave the EU, in line with an estimate from HSBC.

The bank’s strategists warn that the UK’s large current account deficit is funded by inflows of capital from overseas. A Brexit would likely cause inflows to dry up (indeed, you could argue that they’re fraying already), driving a sharp devaluation of the pound.

They note:

Last week, BoE Governor Mark Carney reiterated that the UK’s current account deficit meant that the UK was dependent on inflows of foreign capital – in effect that the UK economy relied on the “kindness of strangers”.

Brexit would “increase uncertainty, weigh on the UK outlook and raise concerns of foreign investors,” resulting in “an abrupt and total interruption to incoming capital flows”.

Goldman Sachs number crunchers calculate that the UK current account deficit of 3.7 per cent of GDP, if balanced by out by sterling depreciation (rather than a drop in domestic demand), would require a 15-20 per cent drop in the value of the pound.

This means a pound would buy $1.15-$1.20, instead of $1.46 currently, or one euro would buy £0.90-£0.95 instead of £0.76 at the moment. Cancel that overseas shopping trip.

It’s not a flat-out negative; a drop in sterling would cheer the country’s exporters. But if it were rapid, it could be destabilising.

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