Re: [asa] Trees don't lie

From: George Murphy <>
Date: Mon Mar 23 2009 - 09:51:48 EDT

Glenn -

Very quickly, & as far as I have anything to contribute winding this up for
now -

It's necessary distinguish between two things. (a) The basic dynamics of a
complex system which, to the extent we can model it mathematically, require
nonlinear equations, and (b) the analysis of some important data about the
system which may use various math approximations. Think of the difference
between Newton's laws and Kepler's. Many (though not all) nonlinear systems
display sensitivity to initial conditions so that we can't predict the
future state (i.e. the precise values of positions & velocities for
mechanical systems) far into the future. But we can analyze data using
various approximations and assumptions in order to estimate certain
important facts about the future bahavior of the system. The latter seems
to me to be what Hubbert did quite successfully.

(BTW, it's easy from the math at the site I gave to see why the peak occurs
at the point where half the initial reserve has been exhausted - in this
approximation of course.)

About the other systems (elections, MLB) I didn't say I "wanted" equations.
I said earlier that I don't think we can have a complete math description of
such things. But to the extent we do, or can use a math metaphor, they're
nonlinear. & there are knowledgeable people who can make predictions that
are not perfect but are pretty good statistically. They don't do that by
solving equations though. I agree with Plato that God is a mathematician
but he has other interests as well!


----- Original Message -----
From: "Glenn Morton" <>
To: "George Murphy" <>
Cc: "asa" <>
Sent: Sunday, March 22, 2009 10:56 PM
Subject: Re: [asa] Trees don't lie

> Hi George,
>> Again you of course know a lot more about oil production than I. But
>> when I take a quick look at a discussion of Hubbert's math at
>> I
>> see a slightly wavy curve of P/Q vs Q and the phrase "Let us fit a
>> straight line to this set of dots from 1958 on ..." . Now I understand
>> that Hubbert's original analysis was more complex but what's being done
>> here looks like making the simplest - linear - mathematical description
>> of what is really a pretty complex phenomenon in order to predict, not
>> the precise future state of the system but one crucial feature of
>> particular interest. I would be very surprised if the real dynamics of
>> oil production - if we could have a precise mathematical description - is
>> really describable with strictly linear equations. If it is, please
>> enlighten my ignorance by showing me that it is or referring me to an
>> appropriate source.
> .
> I will absolutely grant that you know more math than I. But, Hubbert's
> equation works and it is linear. The situation in oil production is
> complex only because of political decisions made by country leaders to
> restrict production or open the taps. Hubbert predicted a world peak oil
> in 1995. The only reason that that prediction didn't happen was because in
> the late 1970s and early 1980s, the world became incredibly more energy
> efficient due to the high prices of oil. But all that did was push the
> peak back about 10-15 years. I think we have peaked because of the
> current down turn. We will never catch up again with the decline because
> we are not drilling as much now. we were barely keeping up with production
> when we were drilling all out. Now that we aren't, world oil supply,
> defined as the amount of oil coming to market per day will decline rather
> quickly. Buckle your belts.
>> Similarly for the other systems I mentioned. What is the justification
>> for saying that the dynamics of a presidential election or a MLB season
>> are linear? To the extent that the term is meaningful, I suspect that
>> the dynamics of all complex systems involving human beings are
>> "nonlinear." A group of 50 Indians confronting 50 Pakistanis isn't just
>> 50 times a 1 on 1 meeting between an Indian and a Pakistani.
> I didn't say that the presidential election was linear.
>> In discussing elections it's significant that you put "equation" in
>> quotes - and never actually write down any. That's because you don't
>> have any. You have relationships that to some extent are
>> semi-quantitative but you don't have A = B relationships. & unless you
>> do, the terms "linear" & "nonlinear" can be used only in the loose (but I
>> hope meaningful) way I did in the previous paragraph. & since you don't
>> have real equations, the concepts of chaos theory can also be applied
>> only in a loose way - which is not to say that they might not be of some
>> value if you're careful.
> George, those are the kinds of systems that Tetlock studied--those lacking
> the kinds of equations you seem to want. That is why experts aren't any
> good.

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Received on Mon Mar 23 09:52:47 2009

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