How could banks have persuaded themselves, their shareholders and the public that they were making so much money when in reality they were losing it? The history of financial deception and self-deception is as old as humanity, but a few themes recur. A Ponzi scheme offers a high return using the funds of newcomers to make payments to earlier subscribers, and collapses when the supply of suckers runs out. The New Economy was the greatest of Ponzi schemes. It has been different this time. But not so different.

I have several times in this column described the Taleb distribution of regular small profits interspersed by large losses. Taleb distributions are the basis of the carry trade – which exploits interest rate differentials – and many types of statistical arbitrage. Taleb distributions are exploited by traders in hedge funds and at proprietary trading desks.