What is System Dynamics?

System dynamics is a methodology for studying and managing complex feedback systems, such as one finds in business and other social systems. In fact it has been used to address practically every sort of feedback system. While the word system has been applied to all sorts of situations, feedback is the differentiating descriptor here. Feedback refers to the situation of X affecting Y and Y in turn affecting X perhaps through a chain of causes and effects. One cannot study the link between X and Y and, independently, the link between Y and X and predict how the system will behave. Only the study of the whole system as a feedback system will lead to correct results.

The methodology:

	identifies a problem,
	develops a dynamic hypothesis explaining the cause of the problem,
	builds a computer simulation model of the system at the root of the problem,
	tests the model to be certain that it reproduces the behavior seen in the real world,
	devises and tests in the model alternative policies that alleviate the problem, and
	implements this solution.

Rarely is one able to proceed through these steps without reviewing and refining an earlier step. For instance, the first problem identified may be only a symptom of a still greater problem.

The field developed initially from the work of Jay W. Forrester. His seminal book Industrial Dynamics (Forrester 1961) is still a significant statement of philosophy and methodology in the field. Since its publication, the span of applications has grown extensively and now encompasses work in

	corporate planning and policy design
	public management and policy
	biological and medical modeling
	energy and the environment
	theory development in the natural and social sciences
	dynamic decision making
	complex nonlinear dynamics

What is the relationship of Systems Thinking to System Dynamics?

Systems thinking looks at the same type of problems from the same perspective as does system dynamics. The two techniques share the same causal loop mapping techniques. System dynamics takes the additional step of constructing computer simulation models to confirm that the structure hypothesized can lead to the observed behavior and to test the effects of alternative policies on key variables over time.

What is the System Dynamics Society?

The System Dynamics Society is an international, nonprofit organization devoted to encouraging the development and use of systems thinking and system dynamics around the world. With members in fifty-five countries, the Society provides a forum in which researchers, educators, consultants, and practitioners in the corporate and public sectors interact to introduce newcomers to the field, keep abreast of current developments, and build on each other's work.

Contact Information

For information, the beer game, bibliography of System Dynamics, or older back issues of our journal please contact Roberta L. Spencer, Executive Director:
   Telephone
        518 442-3865
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        518 442-3398
   Postal address
        The System Dynamics Society
        Milne Hall 300, Rockefeller College
        135 Western Avenue
        University at Albany
        Albany, NY 12222
        USA
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Last edited by JP 1/1/08

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