In a message dated 9/24/00 11:46:06 PM, hal@finney.org writes:
>This means basically that you have a 20% less chance of dying in any
>given year today than you did in 1980. That's a substantial increase,
>but it's been a pretty stable trend throughout this century. Figure 1
>in the PDF file shows the trend since 1930.
>
>The longevity statistics don't show such a dramatic improvement, I suppose
>because the chance of dying gets to be so high in the 70s and 80s that
>few people live beyond that, even if there is improvement in survival.
On the Gompertz curve, which is pretty good for people, mortality
doubles once per period with advancing age. The period for people is
about 8 years. Skipping some mathematical niceties, if you halve the
mortality rate you increase population lifespan by one doubling period.
So you have to reduce mortality by half to extend lifespan by 8 years.
20% should only give us 3 years or so (8*ln(0.8)/ln(0.5)). So what you see
is pretty much what's expected.
If we want to double lifespan this way, we need to reduce mortality by
1000-fold. Tall order, although certainly imaginable.
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