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Computation and the Human Predicament

The Limits to Growth and the limits to computer modeling

Brian Hayes

System Dynamics

The Limits to Growth lists four authors (Donella H. Meadows, Dennis L. Meadows, Jørgen Randers and William W. Behrens III) as well as a project team with 17 members, but the principal architect of the modeling scheme presented in the book is not among these individuals. He is Jay W. Forrester, who arrived at the Massachusetts Institute of Technology in 1939 as a graduate student in electrical engineering and who is there still, almost 75 years later, as professor emeritus. Forrester’s early work was on automatic control and servomechanisms. Later he built the largest digital computer of its time and invented magnetic core random-access memory, which dominated the industry for 20 years.

In 1956 Forrester moved across campus to the Sloan School of Management, where he began applying ideas from control engineering—particularly the idea of feedback—to problems of business. For example, he explained cyclic waves of hiring and layoffs as an “overshoot” phenomenon, where managers responded too late or too vigorously to changes in sales or inventory.

Feedback loops and the risk of overshooting became recurrent themes in a methodology that Forrester named system dynamics. He was soon extending the scope of the technique: His book Industrial Dynamics, on the management of companies, was followed by Urban Dynamics, on the management of cities.

In 1970 Forrester attended a meeting of the Club of Rome, a loosely organized “invisible college” on the lookout for novel approaches to social and environmental problems. On the flight home he sketched a system dynamics model of the world economy and ecosystem. A few weeks later he had a working prototype, which came to be known as World2. The Club of Rome proposed to sponsor this work, but Forrester chose to continue his project independently; a year later he published his findings in World Dynamics. Meanwhile, his colleague and former student Dennis Meadows assembled a team for the Club of Rome project. Their version of the model is World3.

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