In a frosted-glass cubicle in the Cass Business School on the edge of the City of London, David Blake, an earnest, greying professor of pensions economics, is waving a chart. It looks similar to the graphs that economists often use to estimate asset prices or currency movements: a fan of colours depicts probabilities of events occurring until 2050. "We modelled this on the Bank of England's inflation graphs," explains Blake, with pride.

But these statistics do not relate to anything as mundane as prices. Rather, they are about the more gruesome topic of death. Specifically, Blake is predicting how long our children, and children's children, will live - and his conclusions are striking: over the past century, life expectancy in the western world has not only risen, but the rate of increase has accelerated. While someone in the 1840s lived, on average, to 40, today's generation can expect to hit 80, "and for our grandchildren, it could be 160," says Blake, stabbing a pale green corner of his fan chart.