[ExI] Serious topic
anders at aleph.se
Mon Feb 28 10:29:23 UTC 2011
Keith Henson wrote:
I'm having serious problems with Hubbert curves, for the same reason I
have become less happy with using Moore's law for long range prediction.
Just like Bass technology diffusion curves they fit data very well in
retrospect. But when used to extrapolate the future they seem too
unstable: the predicted peaks or sigmoids jump all over the place due to
noise in the data.
When you have a fairly well developed curve (i.e. you are far beyond the
hump of a peak or the inflexion point of a sigmoid) extrapolation is
robust. But before that - at the hump or inflexion point, or even a bit
after - the extrapolation is almost useless. It is worth testing it
yourself with a toy model with noisy data, the effect is a bit
surprising. Those confidence intervals get very wide.
It is better to try to shore things up using other kinds of data or
modeling. UK oil production is clearly moribound, but it is also a
particular rather small pocket. Oil reserve data is famously uncertain
and biased by various interests. It might be more revealing to look into
how the markets are investing long-term.
Future of Humanity Institute
James Martin 21st Century School
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