In a report published on Thursday, the ratings agency’s senior economist, Boris Glass, said the world’s fifth biggest economy would have been about 3% larger by the end of 2018 if the country had not voted in a June 2016 referendum to leave the bloc.

Quarterly growth rates would have averaged about 0.7%, rather than 0.43%, he said.

“Immediately after the referendum, the pound fell by about 18%. This was the single most pertinent indicator of the impact of the vote and the drag it created, via inflation, has been spreading through the economy,” he said.

As imports became more expensive, inflation started to rise, dampening household spending. S&P estimated inflation was 1.8% higher than it would otherwise have been by the third quarter of 2017.

The estimate in sterling is slightly lower than an assessment by Goldman Sachs earlier this week, which pegged the cost to the economy at about 600 million pounds per week. That equates to 7.8 billion pounds a quarter, according to Reuters calculations.