Tom Fiddaman's System
Dynamics Model Library
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This library contains replications of many classic models from system dynamics
and related fields. Citations are provided. Unfortunately I don't know of online resources for most of the articles,
but links are provided where possible. MIT theses are now available online through MIT
Document Services. Many classic SD publications are available through
Pegasus Communications.
Many of the models in this library were recreated from published works by students
in the MIT Sloan School's PhD Seminar in System Dynamics. Where credit is unknown, thanks should go to Rogelio
Oliva, Scott Rockart, Nelson Repenning, Ed Anderson, Liz Krahmer, Hank Taylor, and several other MIT students for
the arduous process of reconstructing these models from published sources. Be forewarned that, since most of these
models are replications, it's possible that they contain errors introduced in the publication or reconstruction
process.
Since Vensim is now binary-compatible across platforms, I'm standardizing on Vensim
5.0 file formats for this library. Vensim files are generally included in both binary (.vmf) and text formats (.mdl and .vgd, among
others); you should have no trouble using them on either platform. There are some differences in floating point
math between the two platforms, so you may find differences in output or fp errors I haven't discovered that occur
only on one platform. Vensim models with many supporting .cin, .prm, .lst, and similar files are sometimes .zipped
for convenience. You may need to translate carriage returns and linefeeds to your platform's standard before using
these files. Many Vensim models can be run and edited with Vensim Personal Learning
Edition (free); models with arrays, optimization, or other advanced features
may be browsed and run with the Vensim
Model Reader, but require purchase of Vensim DSS for editing.
A few models are also available in ithink format. ithink files are in Macintosh
version 3.0.5 format, binhex encoded.With appropriate file naming (i.e. use .itm or .stm as the file extension)
you should be able to open them on the Windows platform as well, though I've never tried. Windows users may need
a utility to remove the binhex encoding. ithink (and its identical twin, STELLA) are available in several versions
for academic and business users from High
Performance Systems. You may be able to read and run models using a newer
ithink/STELLA demo or runtime version (free), but I haven't tried. If you move ithink/STELLA files from Windows
to a Mac, you may need to use a utility such as FileTyper to reset the file type (try ithm) and creator (try ithn)
to something the application will recognize. Note that these tags are case-sensitive.
The models in this library may be freely used and distributed, provided that you
suitably acknowledge the hard work of the authors and implementors who created these files.
If you have trouble downloading or decompressing any of these models, please let
me know at tom@vensim.com. I'll try to patch things up as quickly as possible.
Catalog
- (You can also browse
directly)
Recent Additions
- By Tom Fiddaman. See publications for documentation and related articles.
- John D. Sterman,
1981. PhD Dissertation, MIT Sloan School of Management
Climate, Energy & Environment
- Replicated by Tom Fiddaman from: Nordhaus, William D. (1994). Managing the Global Commons. Cambridge, MA: MIT
Press. The model originally appeared as: Nordhaus, William D. (1992). An Optimal Transition Path for Controlling
Greenhouse Gases. Science, 258(20),
1315-1319, and: Nordhaus, William D. (1992). The "DICE" Model:
Background and Structure of a Dynamic Integrated Climate-Economy Model of the Economics of Global Warming Discussion Paper No. 1009. Cowles Foundation for Research in Economics at Yale University.
See also: SEDAC
Thematic Guide and a review of Managing the Global Commons. Browse equations in HTML
- From: Fiddaman, Thomas (1995). Formulation
Experiments with a Simple Climate-Economy Model. In 1995 System Dynamics
Conference, Plenary Papers, Tokyo, Japan. Tests an explicit energy sector with endogenous technology, alternative
carbon cycles, and behavioral decision rules in the DICE framework. Browse equations in HTML
- Replicated by Tom Fiddaman from: Hatlebakk, Magnus, & Moxnes, Erling (1992). Misperceptions
and Mismanagement of the Greenhouse Effect? The Simulation Model . Report
# CMR-92-A30009, December). Christian Michelsen Research.
- Replicated by Tom Fiddaman from: Wang, Qifan, Brian McKeller, Randy Schweickart,
and John Sterman (1983). A Simple Model of Energy Dynamics D-3484. MIT System Dynamics Group. Note that this model does not perfectly replicate the
behavior shown in the paper, and may contain errors. A version with a modified investment allocation structure,
by Tom Fiddaman, is also available.
- Replicated by Tom Fiddaman from: Moxnes, Erling (1992). Positive Feedback Economics
and the Competition Between 'Hard' and 'Soft' Energy Supplies. Journal
of Scientific and Industrial Research, 51(March), 257-265.
- Forrester's classic World Dynamics (1971), the predecessor to World3. Now available
through Productivity Press. This version is from the standard Vensim distribution package.
- A dynamically interesting economy-environment model (see critique). Alexandra
Milik, Alexia Prskawetz, Gustav Feichtinger, and Warren C. Sanderson, "Slow-fast Dynamics in Wonderland,"
Environmental Modeling and Assessment 1 (1996) 3-17.)
- Forrester's classic Urban Dynamics (1969). Now available through Productivity
Press. This version is from the standard Vensim distribution package.
- The updated version of the model behind The
Limits to Growth. From Donnella H. Meadows, Dennis L. Meadows, Jorgen
Randers, Beyond the Limits. Post Mills, VT: Chelsea Green Publishing Co. 1991. This version is from the standard
Vensim
distribution package.
- Replicate by Paulo Goncalves from Chapter 6 of the book: Toward
Global Equilibrium: Collected Papers, by William W. Behrens III.
Business & Economy
- Replicated by Tom Fiddaman from: A Behavioral Analysis of Learning Curve Strategy,
John D. Sterman and Rebecca Henderson, Sloan School of Management, MIT and Eric D. Beinhocker and Lee I. Newman,
McKinsey and Company.
- Replicated by Tom Fiddaman from: Stephen C. Graves, Massachusetts Institute of
Technology, A Single-Item Inventory Model for a Non-Stationary Demand Process, MSOM 1:1, 1999.
- The first major model (Chapter 15) from Forrester's classic Industrial Dynamics
(1961), available through Productivity Press. Replicated by Tom Fiddaman
- John Morecroft's implementation of Jay Forrester's Market Growth model, replicated
by ??? from: Morecroft, J. D. W. (1983). System Dynamics: Portraying Bounded Rationality. Omega, 11(2), 131-142. See also: Forrester, J. W. (1968). Market Growth as Influenced by Capital
Investment. Industrial Management Rev. (MIT), 9(2), 83-105.
- John Morecroft's model of a sales organization, replicated by Liz Krahmer, MIT
System Dynamics Group.
- Replicated by Julio Gomes and David Sirkin, MIT System Dynamics Group, from Roger
Hall's ASQ article, "The Rise and Fall of the Saturday Evening Post."
- Replicated by Rogelio Oliva from: Sterman, John D. (1980). The
Use of Aggregate Production Functions in Disequilibrium Models of Energy-Economy Interactions
D-3234. MIT System Dynamics Group. Translated to Vensim by Tom Fiddaman.
- John Sterman's model of the economic long wave, replicated by Martin Grossman
from
Sterman, John (1984) "A Behavioral Model of the Long Wave," Journal
of Ecconomic Behavior and Organization, v. 6, pp. 17-53.
Sterman, John (1989) "Deterministic Chaos in an Experimental Economic System,"
Journal of Ecconomic Behavior and Organization,
v. 12, pp. 1-28.
- Replicated by Ed Anderson and Liz Krahmer from: Meadows, D. L. (1970). Dynamics of Commodity Production Cycles. Cambridge
MA: Productivity Press.
- Replicated by Scott Rockart and Liz Krahmer from: Mass, N. J. (1975). Economic Cycles: An Analysis of Underlying Causes.
Cambridge MA: Productivity Press.
- Provided by Nathan Forrester See: Forrester, N.B. (1982) A
Dynamic Synthesis of Basic Macroeconomic Theory: Implications for Stabilization Policy Analysis. PhD Dissertation,
MIT Sloan School of Management.
- Replicated by Tom Fiddaman from an SD Review article by Gilbert Low. See also:
Richardson, G. P. (1991). Feedback Thought in Social Science. University of Pennsylvania Press.
Science
- Replicated by Hank Taylor from Jeppe Sturis, Kenneth S. Polonsky, Erik Mosekilde,
and Eve van Cauter. Computer Model for Mechanisms Underlying Ultradian Oscillations of Insulin and Glucose. Am. J. Physiol. 260 (Endocrinol. Metab. 23): E801-E809,
1991.
- Replicated by Tom Fiddaman from Jensen, K.S., Mosekilde, Erik, and Holstein-Rathlou,
N. Self-Sustained Oscillations and Chaotic Behavior in Kidney Pressure Regulation. In I. Prigogine and M. Sanglier,
eds., Laws of Nature and Human Conduct.
Brussels: Taskforce of Research Information and Study on Science. See also a related abstract. Includes a useful example of
the Vensim FIND ZERO function (a simultaneous equation solver), phase plots, and Poincare maps and sections. See
header of .mdl file for details concerning use.
- Implemented by Tom Fiddaman.
- Replicated by Tom Fiddaman from: ???
Miscellaneous
- Statistics for describing the fit of model behavior to historical data. A Vensim
model accompanies the paper, Oliva, Rogelio, A Vensim Module to Calculate
Summary Statistics for Historical Fit, MIT System Dynamics Group D-4584
in Acrobat format. A similar but older ithink model is also available, courtesy of Nelson Repenning and John Sterman. See also: Sterman,
J.D., (1984) Appropriate Summary Statistics for Evaluating the Historical Fit of System Dynamics Models. Dynamica, 10 (Winter), 51-66.
- Replicated by Rod Macdonald, SUNY-Albany, from Coyle, R. G. (1992). “A system
dynamics model of aircraft carrier survivability.” System Dynamics Review 8(3): 193-213.
- Replicated by Tom Fiddaman and Anjali Sastry from Daniel Levinthal and James
G. March (1981) A Model of Adaptive Organzational Search. Journal of Economic
Behavior and Organization 2. pp. 307-33. See header of .mdl files for
details of model implementation and use.
- Jack Homer's worker burnout model, from Homer, J. B. (1985). "Worker Burnout:
A Dynamic Model with Implications for Prevention and Control." System Dynamics Rev. 11: 42-62. Required reading
for overachievers. This version is from the standard Vensim distribution package.
Hit List & Vaporware Dept.:
CONNECTICUT-Yohe
- At one time I replicated 95-99% of this model from Yohe, Gary and Rodney Wallace
(1996). Near Term Mitigation Policy for Global Change under Uncertainty: Minimizing the Expected Cost of Meeting
Unknown Concentration Thresholds. Environmental Modeling and Assessment
1. pp. 47-57. However, I was never able to resolve a few structural and
parameter uncertainties and thus it is not posted here. Contact me if you still would like to obtain a copy. See
also SEDAC
Thematic Guide.
Guidelines for Replication
I can't guarantee that I'll accept submissions to this library, but if you have
a nice replication of a published work (especially one on my hit list), or an original model that's been published
somewhere, I'll consider it for inclusion here (with credit, of course). An ideal model will observe the following
guidelines:
- Vensim format (any version; preferably no external function library dependencies)
- Clean diagram (hopefully with views corresponding to published diagrams)
- Clean variable names (if original uses short names, append clear names at the
end, e.g., "DCD" becomes "DCD Developer Cost of Disposal"
- Numerically correct (replicates original results, or documents discrepancies)
- Custom graphs predefined where useful
- .CMD, .CIN, or other files to automate scenario/experiment replication
