System Dynamics

System dynamics is a method for studying the world around us. Unlike other scientists, who study the world by breaking it up into smaller and smaller pieces, system dynamicists look at things as a whole. The central concept to system dynamics is understanding how all the objects in a system interact with one another. A system can be anything from a steam engine, to a bank account, to a basketball team. The objects and people in a system interact through "feedback" loops, where a change in one variable affects other variables over time, which in turn affects the original variable, and so on.

An example of this is money in a bank account. Money in the bank earns interest, which increases the size of the account. Now that the account is larger, it earns even more interest, which adds more money to the account. This goes on and on. Another example of a simple feedback loop which we have all experienced is adjusting the water tap to reach a desired temperature. You turn the faucet, feel the temperature, and compare it to the desired temperature. You continue to adjust the water, with smaller and smaller adjustments, until you reach the desired temperature.

What system dynamics attempts to do is understand the basic structure of a system, and thus understand the behavior it can produce. Many of these systems and problems which are analyzed can be built as models on a computer. System dynamics takes advantage of the fact that a computer model can be of much greater complexity and carry out more simultaneous calculations than can the mental model of the human mind.

Two examples of important questions addressed by system dynamics models are:

• What causes American cities to degenerate? And what can be done to revitalize these stagnant urban areas? (Forrester, Jay W. Urban Dynamics. The MIT Press, Massachusetts 1969.)
• Can the Earth's resources support mankind, with its present economic and population growth rates, in the next millennium? What can be done to confront possible global collapse? Is a sustainable future possible? (Meadows, Donella and Meadows, Dennis and Randers, Jorgen and Behrens, William W. The Limits to Growth. Universe Books. New York: 1972. and Meadows, Donella and Meadows, Dennis and Randers, Jorgen. Beyond the Limits. Chelsea Green Publishing Company. Vermont: 1992.)

We have selected several introductory documents that might help you to find out more about the field of system dynamics. They provide an overview of the development, use, and educational applicability of system dynamics. These documents are in a format which is readable with the Adobe Acrobat Reader. If you need help with it, visit the Adobe Site or read our help page.

• The Beginning of System Dynamics (D-4165-1) [34K], by Prof. Jay W. Forrester, provides a personal point of view about the development of system dynamics.
• Learning through System Dynamics as Preparation for the 21st Century (D-4434-1) [41K], by Prof. Jay W. Forrester, explains the advantages of a system dynamics education for the future.
• System Dynamics Meets the Press (D-4143) [27K], an excerpt from The Global Citizen by Donella H. Meadows, discusses the experiences of the author in introducing system dynamics to the public and the mass media.
• System Dynamics for Kids (D-4489-1) [19], by Jim Hight, is an overview of the use of system dynamics computer modeling in K-12 education.
• System Dynamics and Learner-Centered-Learning in Kindergarten through 12th Grade Education (D-4337) [49K], by Prof. Jay W. Forrester, presents the author's views on how system dynamics may improve classroom learning.

Road Maps: A Guide To Learning System Dynamics teaches the basic principles of system dynamics and introduces you to modeling and simulation.

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