# Re: poly: Computers induce fast growth?

From: Robin Hanson <hanson@econ.berkeley.edu>
Date: Thu Sep 10 1998 - 20:40:36 PDT

Hal writes:
>: ... If the current mode were to last through a
>: WP factor the same as one of the last three modes, it would last until
>: either 1988, 2024, or 2060. And if the next DT factor were the same as
>: one of the last four DT factors, the next doubling time would be either
>: would be .1, 1.2, 2.0, or 3.5 years. This suggests dramatic change within
>: the foreseeable future!
>
>I would find this extrapolation more convincing if there were some
>stability in the DT and WP columns. Instead they vary amongst themselves
>by more than an order of magnitude. And with only four or five samples,
>the next line could easily be yet another order of magnitude larger or
>smaller.

I interpret this as saying that historical records can't get us that far;
a lot of uncertainty remains. But at least you can start to indentify
some things as implausible. For example, two orders of magnitude seems
unlikely, so scenarios where doubling comes every day look out of whack.

>It's also not clear that WP is the right "clock" for timing transitions.
>Again, the lack of consistency is disturbing. I suppose one thing you
>could do is to depict "number of doublings", which would just be the
>log base two of WP, giving >0.9, 5.1, 7.4, 2.9, >3.6.

Yes, that looks more intuitive.

>OTOH we could hardly rule out 10 or 15 doublings, either, carrying us
>well into the 22nd century.

Well "rule out" is too strong, but you could shift the "burden of
argument" against those who suggest another century of business as ususal.

>As for the doubling times, if we extrapolate the last three entries in
>the DT column it wouldn't be that surprising to see a further factor
>of 3 decrease in the DT factor, making the new DT factor be 1.5 and the
>new doubling time be 10 years. This would not be dramatic.

I'd find it a little suprising, as I find the decreasing DT model implausible.

>Overall it seems that the paucity of data makes it difficult to rule
>out any a priori plausible scenario for economic growth rates over the
>next couple of centuries. We could switch to a doubling time of .1
>year tomorrow (1000 fold growth per year) or we could see only moderate
>changes over the next 300 years, all basically consistent with the data.

These are all reasonable criticisms, but don't you find this framework at
least a useful resource when thinking about what speculations are how
plausible? Given how little else we have to go on, I find it comforting
to at least of some sort of empirical context to work with.
Received on Fri Sep 11 03:27:45 1998

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