"February is the worst month to be born in. Those people live a couple of years less than those born in August." Bad news for winter babies, but Stephen Richards, the Prudential's head of mortality risk, is used to gloom. His job is to research when - and why - we die.

The commercial risk-assessment aspect of the job is vital for Prudential, which has some £20bn of annuity liabilities and pays out income to 750,000 annuity holders a year. But the side-effect of his team's number-