The US productivity “miracle” – one of the defining economic developments of modern times – is looking a shade less miraculous than it did a month ago.

Following a series of revisions to recent historic data, economists are pondering whether to reduce their estimates of the speed at which the world’s biggest economy can grow without generating inflation. Many have done so already, cutting their assessments of US potential growth by about 0.25 per cent. This may not sound a lot but, compounded year after year, it adds up to a significant loss.