June 24 will be a day of superlatives for the pound, whichever way Britain votes.
The day after next week’s referendum on European Union membership, the pound will either sink to the lowest level in more than three decades or climb towards the highest this year, according to a Bloomberg survey of economists. 
Most see a drop below $1.35 if Britons decide to leave the bloc on June 23, while the median estimate following a victory for the status quo is for it to jump to as high as $1.50.
A Brexit vote “would certainly be a shock event for currency markets in a way that’s pretty unusual outside of major financial crises,” said Michael Bell, a global market strategist at JPMorgan Asset Management in London, which manages $1.7tn in assets. “The pound would fall very sharply.”
The median estimate in the survey was for the pound to drop to between $1.30 and $1.35 a day after a vote to ‘Leave,’ while a range of $1.45 to $1.50 was seen if the ‘Remain’ campaign triumphs. Sterling was 0.9% weaker at $1.4122 in London yesterday.
Preparing for either scenario is important for investors as polls suggest the result of the vote is too close to call. In the past few weeks, the currency has been jolted by a series of surveys showing one or the other side in the lead, while traders are bracing for even more volatility as June 23 approaches, with a two-week measure rising to a record high yesterday.
A decline to $1.30 would represent a drop of about 8% from the current level. A move of that degree on the day following the referendum would be the biggest on record, surpassing tumbles seen during the 2008 financial crisis and on Black Wednesday in 1992, when the British government decided to let the pound float freely. 
And that’s not even the worst case scenario - 14 out of 32 economists surveyed expect sterling to fall below $1.30, with five of them seeing it lower than $1.20.
The UK currency has already dropped more than 4% this year as investors assess the risks of an exit. It fell to a seven-year low of $1.3836 in February after Prime Minister David Cameron announced the date of the vote, and has since fluctuated as polls suggested both sides may still prevail.
Sterling plunged to its lowest since April against the dollar yesterday after polls published in the past week showed the ‘Leave’ campaign leading by as much as 10 percentage points. Others have shown a more balanced contest, with many voters still undecided.
A decline below $1.3503 would push the pound to the lowest since 1985. Such a severe depreciation in the currency risks causing repercussions for the wider UK economy, from the soundness of its current account to faster inflation. Weakness in the economy could also delay interest-rate rises from the Bank of England, according to JPMorgan AM’s Bell.
“Interest rates are likely to go up much later than they otherwise would” should the country leave the world’s largest single market, he said. Meanwhile a weaker economy would reduce the UK’s attractiveness for foreign investors, further weighing on the pound, he said.
While the upside to the currency if the UK votes to stay is set to be smaller, according to Bloomberg’s survey, a move to $1.50 still indicates a bounce of more than 6% from current levels. However, only nine out of 31 economists see it going above this level, and seven see it trading close to current levels between $1.40 and $1.45.
Some strategists and investors predict the rally in the pound would be fleeting if there’s a “Remain” vote, as the UK economy faces difficulties beyond the referendum. The pound’s rally may be even smaller if there’s a tight vote to stay, according to Richard Benson, managing director and co-head of portfolio investment in London at Millennium Global Investments, which manages about $16bn. 
He sees sterling strengthening 3% if Britons decide to stay on June 23 provided it’s a “solid” victory for the “Remain” camp.
“It could be less than that if the results are very close” as “people will talk about political squabbles” and speculate about the consequences for David Cameron’s political future, Benson said.