Re: Exponential function

["Van E. Neie" <ven@physics.purdue.edu>]

> 900 years into the future, it should be possible to retrodict into
> the past.  If the population now is about 5.4 billion and it is
> doubling about every 40 years or so then 600 years ago, in the
> fourteenth century the population should have been less than
> 200,000.  But I have read that in the fourteenth century the great
> epidemic of black plague killed in Europe alone about 25,000,000
> people, making for a world population of 200,000 a truly dismal
> retrodiction from the exponetial function.  So, I would say that
> the exponetial function is quite limited in its applicability to
> human population growth, except as a scare tactic via the prestige
> of mathematical statements.
The doubling time is 70/p, where p is the percentage growth.  This number
(p) has not been a constant.  In fact, for the world it was about 2% in
1960, but is now about 1.6% or so (I haven't seen the latest figures).
Scare tactics?  Well, maybe, but there will never be a concerted effort
to do something about the problem unless one sees the drastic consequences
of NOT doing something.  When the numbers are large the problem is con-
siderably worse because changes that might seem significant turn out to do
nothing.  In 1975 a typhoon devasted Bangladesh, with the estimate being that
roughly 500,000 people were killed.  At that time the birth rate was such
that this number of people would be replaced in approximately 45 days!

If not scary, at least these kinds of data ought to be sobering.

Van Neie


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Van E. Neie                                      ven@physics.purdue.edu
Purdue University                                
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