Spike Jones, <firstname.lastname@example.org>, writes:
> Question please: is there a term for the point in history where
> life extension technology is increasing our life expectancy one
> year for each year one lives, such that the mathematical
> expectation of ones remaining life stops decreasing? That
> point I suspect is 20-30 yrs away.
That's a good question. Maybe you could call it the "longevity
break-even point" or something similar. Or you could define the
"longevity ratio" as the rate at which longevity is increasing
per elapsed time.
One thing to keep in mind, official life expectancies are calculated by
taking the death rate at each age TODAY, and combining them. This tells
you how long person born today would live if, as he aged, he had the same
probability of death at each age that a person of that age does today.
This is a pretty unrealistic model because even if medicine (or whatever
it is which gets credit for longevity) were somehow frozen at today's
level, some of the health improvements at younger ages would probably
cause decreased death rates when older, just because of less damage to
the body. However it is a figure that can be derived unambiguously
from current statistics, and it does serve as a benchmark to measure
longevity improvements from one decade to the next.
"The average American life span rose to 76.5 years in 1997, up from
76.1 years in 1996." http://onhealth.com/ch1/briefs/item,46909.asp.
This would give us a longevity ratio of 0.4 that year. However I think
this may have been be a statistical glitch, I saw something about them
changing how longevity was calculated in 1997. Here is a table from
http://www.cdc.gov/nchs/data/hus_95.pdf, to which I have added the "LR"
or longevity ratio, calculated by dividing the increase by the number
Year Life LR
1950 68.2 0.41
1960 69.7 0.15
1970 70.8 0.11
1980 73.7 0.29
1984 74.7 0.25
1985 74.7 0.0
1986 74.7 0.0
1987 74.9 0.2
1988 74.9 0.0
1989 75.1 0.2
1990 75.4 0.3
1991 75.5 0.1
1992 75.8 0.3
1993 75.5 -0.3
<add two figures from above>
1996 76.1 0.2
1997 76.5 0.4
Obviously there has been considerable variation in the longevity rate
figure from year to year and from decade to decade. The trend has not
been very stable. Generally we have been in the .1 to .3 range for the
last several decades. At this point it looks to me like we would need
a major new breakthrough to start this figure heading up towards 1.0.
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