World Dynamics developed by Jay Forrester (1971) is one of the classic system dynamics models. It is an important model because it has been the basis of the controversial and widely-debated world models used in the Club of Rome's report, also known as Limits to Growth (Meadows et al., 1972; Randers, 2004). 

World Dynamics developed by Jay Forrester (1971) is one of the classic system dynamics models. It is an important model because it has been the basis of the controversial and widely-debated world models used in the Club of Rome's report, also known as Limits to Growth (Meadows et al., 1972; Randers, 2004). 

One way to address this criticism is to transform ECIRN (a constant in the original model) into an exogenous growth function with a 2.5% growth rate.

6.2. Formulate your assumption about substitutability in the model