You might have seen sober and accurate Financial Times reporting of the US economy’s remarkable annualised growth rate of 5.2 per cent in the third quarter of this year. Let me give you an advanced sight of what happened in November. Forget talk of rapid growth or soft landings, the US economy shrank at an annualised rate of around 30 per cent in that month alone. It is so large, President Joe Biden must be toast and it probably spells the end of the American dream.

Don’t worry. I have not lost my marbles. The calculation above is true, but it is not fair. I have taken the US economic performance in November — assumed to have not done much — and calculated that in euros or renminbi after converting US GDP using market exchange rates. Then I annualised the result. The thing that drove the result was the near 3 per cent fall in the US dollar’s value during the month.

You would be right to think this is an absurd way to compare economies, but it is deeply fashionable among people who should know better. Take Mark Carney, former governor of the Bank of England, who said that before the Brexit referendum, the UK economy was 90 per cent the size of the German economy but it had declined to 70 per cent by late 2022. That change was caused by the relative decline in sterling.