Abstract for: Role of Stock constraint in single-stock single-inflow two-outflow System Dynamics model structures

The building blocks of a System Dynamics (SD) model are the stocks and its associated flows. A single-stock model with one inflow and two outflows is one of the many structures used in SD modelling. Typically, a stock assumes homogeneity of its contents in all aspects. However, there are instances of single stock models where there are qualitative differences between the two outflows, for example, Recovered population vs Deaths. This paper analyses validity of such model structures and shows that these model representations are incorrect. Outflows in these cases do not apply a stock constraint and mixes entities of two different qualities in the outflows. The model also underestimates the actual stock value. The study uses an Agent Based Model to arrive at the above conclusions.