[ExI] Serious topic

[Eugen Leitl]

On Mon, Feb 28, 2011 at 10:29:23AM +0000, Anders Sandberg wrote:

> I'm having serious problems with Hubbert curves, for the same reason I  

The basic bell-shape is sound though.

> have become less happy with using Moore's law for long range prediction.  

Projecting Moore into the future is bunk, simply because it's
the result of a simple 2d feature shrink, at simultaneously 
higher entry costs for the next node. 

The only way to give Moore second wind is to leap into 3d, and
I'm very leery expecting just-in-time new technologies.

> 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.

I see little magic in graphs, but in fundamental processes giving
rise to the graphs.

> 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  

Each pocket follows the same curve. Local oil peaks have come and gone,
now we're in a global peak. It's completely expected.

> and biased by various interests. It might be more revealing to look into  
> how the markets are investing long-term.

Markets are chronically poor long-term predictors.

-- 
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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