QUERY Inputs for World3-2003 scenarios (SD6842)

[SDMAIL Jack Harich]

Posted by  Jack Harich <jack at thwink.org>

I’ll be extending the LTG World3-2003 model as part of an analysis. The 
first step is to identify the nodes that vary with the scenarios, find 
the values for each node for each scenario, and then setup the model so 
the scenarios can be easily run.

Vensim ships with the model in VMF format, with 13 CIN files. One would 
expect the CIN files to agree with the third edition of Limits to 
Growth. But unless I’m missing something, they do not.

The model is set for scenario 1. For scenario 2, I’d expect the 
W303S02.CIN file to have the two parameter changes described on page 172 
in the caption to figure 4-12, in the 2004 edition of LTG. But only the 
first parameter is in the file. The parameter to "postulate that 
advances in resource extraction technologies are capable of postponing 
the onset of increasing extraction costs, industry can grow 20 years 
longer" is missing. Running the model with only the first parameter 
changed fails to duplicate the graphs in figure 4-12 for scenario 2. 
Looking in the W303S03.CIN, W303S04.CIN and W303S05.CIN files, the 
missing parameter is not there either.

But it is in Harmut Bossel’s "System Zoo 3 Simulation Models", 2007. 
Page 179 has a beautiful table of 20 parameters for all 10 scenarios. 
The missing parameter is named "investment in obtaining resources time." 
Its value changes from 4000 in scenario 1 to 2002 in scenario 2. This 
makes sense.

But guess what? "investment in obtaining resources time" is not in the 
model file! Looking on page 194 of Bossel, we see the node right at the 
top of the page. But looking in the Vensim model file, on the 
nonrenewable resources page, we see A DIFFERENT VARIABLE!!! The name has 
been changed to "fraction of capital allocated to obtaining resources 1 
table", and the type has been changed from auxiliary to lookup. The two 
models are different! What’s going on here? Are there multiple versions 
of World3-2003?

Once I realized this discrepancy, I thought it was time to stop modeling 
and consult my fellow modelers. Does anyone know if a correct, complete 
table of scenario parameters exists for World3-2003, the version that 
ships with Vensim? Or alternatively, why do the CIN files that ship with 
it seem to disagree with the published model? Do the CIN file numbers 
correspond with the 10 published model scenarios?

If so, then why are there 13 CIN files? Perhaps these are the unnumbered 
experiments discussed after scenario 10? If so, the CIN files 9 and 11 
do not agree with the book’s description of what might be pseudo 
scenario 11 on pages 250 to 251. "industrial output per capita desired" 
is the same in both files. It’s not doubled, as the book describes.

Thanks from a perplexed modeler,
Jack
Posted by  Jack Harich <jack at thwink.org>
posting date  Sun, 30 Mar 2008 19:21:35 -0400