From: Robin Hanson (rhanson@gmu.edu)
Date: Thu Mar 23 2000 - 12:26:57 MST
Hal Finney wrote:
>Robin writes:
> > http://hanson.gmu.edu/longgrow.html
>
>Very interesting paper! A few comments and nitpicks:
Thanks, both for the praise and the criticism.
>This "Doubles of DT" also took me a few minutes to figure out.
I'll try to improve my presentation of this and the other awkward
parts you mention.
>I was puzzled by 2019 as the date the most recent technology "began"
>to dominate, and at first I thought it must be a typo. Later on it is
>explained that technically, by this model, the "old" economy, based on
>agriculture, is still larger than the "new" economy, based on industry.
>Not until 2019 will the new economy grow larger than the old economy.
>
>Is this consistent with economic data? Is the total GWP today from
>agriculture still greater than that from industry?
Good questions. I'll try to take a look at it.
>It also seems questionable whether the industrial revolution can sustain
>a doubling rate of 6.3 years. The figures from the other model of 58
>or 15 years seem more reasonable. Wouldn't we expect something like
>the DJIA to model the growth rate of industry over much of this century?
>I think it had a doubling time of more like 15-20 years, until this past
>decade anyway.
In the middle of the transition (where we still are), the growth rate
is only half of what it will be at the end. So the doubling time of 15
years over the last half century is consistent with the model.
>Also, how do you figure 9.2 doubles of WP for the industrial term?
>You say that this is the number of doubles "during a term's period",
>but when did the period for the industrial term start? I thought you
>would start from 2019.
It actually the doubles of WP at the end of a term's period (assuming
it was the last term), vs. what WP would have been without that term.
I'll try to reword.
>These are amazing graphs, but there are some confusing aspects. I can't
>seem to figure out why, qualitatively, the "next" transition looks
>so different in figure 2 from the previous ones. For all the other
>transitions we see leveling, then a bump, then more leveling. For the
>next transition we just see it take off straight up. Why is it that the
>earlier transitions looked like they leveled off but this one doesn't?
It's a matter of what origin is used for the logs on the X axis.
It is LOG(2050 - date), and if you switch 2050 to something different,
the graph looks different. Happy to send anyone the spreadsheet so
they can play with things themselves.
>For figure 3, it appears to show that this two-week doubling transition
>will lead to an annual growth rate of about 8. But in fact it should
>be something like sixty million? Is this chart showing the log of the
>annual growth rate, or the actual growth rate itself?
It is showing the actual growth rate, but an instantaneous rate, in
annual units. That is, it's showing the number that appears in the
exponent, as the B in Y = A*Exp(B*t).
Robin Hanson rhanson@gmu.edu http://hanson.gmu.edu
Asst. Prof. Economics, George Mason University
MSN 1D3, Carow Hall, Fairfax VA 22030
703-993-2326 FAX: 703-993-2323
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