China and India are poorer than we thought; rich countries produce even more than we realised. Those are the obvious conclusions from an unprecedented exercise, carried out by a World Bank-led coalition.

The “International Comparison Program” attempts to compare the size of the world’s disparate economies on the basis of purchasing power. On this basis, China’s output is just 9 per cent of global gross domestic product, down by more than a third from the previous estimate of 14 per cent. India’s share of global GDP is down from 6 per cent to 4 per cent. The total output share of developing economies is down by a sixth. These are huge revisions to the figures.