edVirtus Reference

What Is System Dynamics?

System Dynamics: Explaining Behaviour Through Feedback, Stocks, Flows, and Delays

System dynamics is a method for understanding how the structure of a complex system generates behaviour over time. It represents accumulations as stocks, changes to those accumulations as flows, and circular causal relationships as feedback loops. Computer simulation is then used to explore consequences that are difficult to infer reliably from verbal reasoning alone.

Jay Wright Forrester developed the approach at MIT in the 1950s while investigating instability in industrial production and supply chains. The field subsequently expanded into business, engineering, public policy, health, ecology, education, energy, and many other domains.

A system dynamics study begins with a problem expressed dynamically: what pattern has occurred, and how should it change? Modellers define a boundary, develop a dynamic hypothesis, represent the relevant feedback and accumulation structure, formulate equations, compare simulated behaviour with evidence, and test possible policies.

The method adopts an endogenous perspective. Instead of explaining undesirable outcomes primarily through external shocks or individual error, it asks whether decision rules, information flows, constraints, and delays within the modelled system can reproduce the observed behaviour.

System dynamics models are purpose-specific simplifications rather than complete replicas. Their value depends on transparent assumptions, dimensional consistency, behavioural and structural testing, sensitivity analysis, and sustained engagement with relevant evidence and stakeholders.

The goal is improved understanding and policy design, not mechanical prediction. A useful model can reveal leverage points, unintended consequences, and conditions under which an apparently successful intervention will be delayed, weakened, or reversed by the wider system.