PREDICTIONS – 10 Years Later - Santa Fe Institute

3. INANIMATE PRODUCTION LIKE ANIMATE REPRODUCTION
In fact, in addition to my daughter’s measurements, the card of the
school nurse had curves already traced out through an accumulation of
statistical data for girls of this region over many years. These curves
looked like the upper half of S-curves. My daughter’s data points fell
systematically on the curve, the final height of which was five feet and
six inches at around sixteen years of age.
Ten Years Later
My daughter’s final height turned out to be five feet ten
inches. It proved both forecasts inaccurate but it is more embarrassing
for the school’s approach than mine. After all, my
forecast was within the error!
Fitting growth curves to measurements of children’s height may not
be the recommended approach for determining their final size. More
accurate methods exist which are based on the fact that children have
been amply observed and measured while growing, and by now there is
a wealth of tables and curves that point to the final height with satisfactory
accuracy.
There may be organisms, however, which grow for the first time in
history so that no record can be consulted on how it happened before. In
such cases, forecasts are useful in spite of significant uncertainties. Let
us consider the great American railway network as an example of a oneof-a-kind
“organism.” Should its growth follow the familiar pattern of a
population? Is its final size predictable?
The answer can be found in Alfred J. Lotka’s Elements of Physical
Biology, published in 1925, at a time when railways were still the primary
means of transportation. 4 Lotka presents a graph of the total
mileage of railway tracks in the United States from the beginning of
railway history until 1918, when mileage had reached 280,000. Despite
not having computers at that time, he superimposes on the data a theoretical
S-curve that passes very closely to all points and shows a 93
percent saturation of the U.S. railway “niche” by 1918, and a ceiling for
a total mileage of about 300,000. I looked up the amount of railway
track laid since 1918; it is about 10,000 miles, which largely confirms
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