System Dynamics Case Study

System dynamics is usually used for an extended period involving considering the highly-aggregated statistics of the parameters being modelled [4]. It considers things as one complete entity instead of splitting a whole system into fractures. The fundamental principal of this methodology is to appreciate how all the individual objects in a structure relate to each other [5], making it possible to identify the behaviour of complex systems [4] that are categorised by mutually dependent, common correlation, data response and circular causality.

System dynamics method comprises of seven main things. They are: Defining the question of interest as a function of time. Attempting to create a representation of the system from different perspectives,

The variables can then be calculated from their original value and the net change over time using Equation 2. x^ ' (t): x(t)=x(t-dt)+dt*x '(t-dt) (2) where: x is the state variable t is the time elapsed during the

This is known as the causal loop diagram. The parameter will flow through the system and ultimately being directed back to its source. Consequently, this influences the primary factor [6]. Factors which affect others in the system are linked by arrows, the direction of the arrow shows the direction of the causation [7]. The arrows will be labelled with polarity, either a positive (+) or negative (-) sign. ‘+’ means the loop is a positive feedback loop and has a reinforcing effect in which the initial action is being reinforced while ‘-’ means the loop is a negative feedback loop and has a balancing effect in which the initial action is being resisted. If a loop has a combination of both positive and negative polarities, it means the loop has more than one possible behaviour [6]. Within a system dynamics model there will also a stock and flow diagram, which is a more descriptive diagram than causal loop diagrams. Causal loop diagrams are focused on the qualitative properties of the system while stock and flow diagrams concentrate on the quantitative properties, enabling connections to be made between components through mathematical equations. Figures 1 and 2 are general causal loop diagram and stock and flow diagrams with their