The news that Warren Buffett is now the world’s richest man led to the predictable round of stories about his frugal habits – the cherry Coke, the well-done steaks and the bungalow in Omaha that has been home for 50 years. There is a point here. Like Bill Gates, whom he has toppled from the top spot, Mr Buffett is primarily interested in the business rather than the wealth that results. Money is a means of keeping score rather than an objective in its own right: the fun, Mr Buffett has said, is watching it grow.

Albert Einstein supposedly observed that the most powerful force in the universe is compound interest, and Mr Buffett’s frugality has enabled compound interest to work its magic. During Mr Buffett’s tenure at Berkshire Hathaway, the S&P 500 index has produced an average total return of 10 per cent. That return reinvested over 42 years will multiply your stake 67 times. But if your investments yield twice as much as that – as Mr Buffett’s have done – your wealth increases not by twice 67, but 67 squared, a factor of 4,500. That arithmetic makes Mr Buffett the richest man in the world.