It is reasonable to worry about Apple after Steve Jobs. He is irreplaceable in a way that almost no businessman ever is.

Mr Jobs, who resigned as chief executive on Wednesday, could hardly leave a company in better condition. In the first nine months of the fiscal year Apple’s operating profit margin was 31 per cent (close to Microsoft’s 39 per cent) and its revenues were 78 per cent higher than in the previous year (Microsoft managed a 12 per cent increase).

The finances reflect a heady combination. There has been a steady flow of superior products. Outsourcing is crucial – the company is set to generate about $110bn of revenue this fiscal year, mostly from hardware, out of about $7bn of plant and equipment. And there is the brand halo, which allows Apple to garner premium prices in highly competitive markets (Microsoft, in contrast, reaps quasi-monopoly profits).