A controversial simulation of the world economy started by Jay W.Forrester in the book World Dynamics, 1971 and developed further by Forrester and Dennis Meadows, both of MIT, in the 1970's. It consists of a system of simultaneous differential equations modelling such variables as stocks, food production and resource depletion. The controversy came about because the prediction of the system, in almost all the runs with different starting variables, predicted a giant population crash - effectively the collapse of civilisation.
Criticisms of the model are varied and touch on the shortcomings of many attempts to model vast complex systems, some are outlined below:
- Narrow overall scenarios - not enough diverse sets of assumptions behind the model, only one narrow band of themes are explored.
- Wrong assumptions - for instance the remaining natural resources are assumed to last 250 years (too short), and that use of resources, and pollution are assumed to rise exponentially with growth (too fast).
- No room for learning - the simulation didn't model increasing knowledge and resourcefulness in humans.
- Too much averaging - The model portrayed a homogeneous world where many variables were spread evenly over the earth, not in geographical variation, like reality.
- Not tested by backcasting on history - the system wasn't honed by trying to model growth in the past few centuries, if so it probably would have 'predicted' collapse after a century even if the starting data was initialised from, say, the 1700's.