.SystemDynamics.WorldDynamics.World3.Scenario_1

Information

This is the original WORLD3 model without any interventions. In the book Limits to Growth: The 30-Year Update it is referred to as Scenario #1.

References:

  1. Meadows, D.H., D.L. Meadows, J. Randers, and W.W. Behrens III (1972), Limits to Growth: A Report for the Club of Rome's Project on the Predicament of Mankind, Universe Books, New York, 205p.
  2. Meadows, D.L., W.W. Behrens III, D.M., Meadows, R.F. Naill, J. Randers, and E.K.O. Zahn (1974), Dynamics of Growth in a Finite World, Wright-Allen Press, 637p.
  3. Meadows, D.H., D.L. Meadows, and J. Randers (1992), Beyond the Limits, Chelsea Green, 300p.
  4. Meadows, D.H., J. Randers, and D.L. Meadows (2004), Limits to Growth: The 30-Year Update, Chelsea Green, 368p.

Simulate the model from 1900 until 2100, and display the same variables as in the book Limits to Growth: The 30-Year Update at page 169:


The results obtained are not exactly the same as those shown in the book Limits to Growth: The 30-Year Update due to the integration algorithm in use. Most Modelica simulation environments uses by default a variable-step / variable-order DASSL algorithm, whereas STELLA, just like the older Dynamo software, uses by default a fixed-step Euler algorithm with a step size of 1 time unit.

A second even more important difference is that my Modelica code treats all variables as real-valued floating-point numbers, whereas the STELLA model treated some variables (e.g., population) as integers, whereas it treated other variables as fixed-point variables with only two significant digits after the comma. This led to a quite noticeable quantization error.

As I didn't see any good reason for unnecessarily mutilating the capabilities of the Modelica simulation environment, I decided not to replicate these features of the STELLA code here.



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