Nigel Lawson, the former chancellor, famously complained about the City of London's "teenage scribblers". Right now it certainly seems that financial markets have short memories. From speculative asset bubbles to using earnings per share enhancement to assess deals, sins of the past are being repeated.

One potential explanation for this recidivism is the youth of market participants. Companies, so the theory goes, are run by old birds capable of remembering historical follies - the average age of a board director of an S&P 500 company is 61. In contrast, the people who scrutinise and value securities are spring chickens, more obsessed with their BlackBerries and next quarter's eps than the long term. Indeed some cheerleaders of the dot- com "new paradigm" were too young to have experienced the old one.