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Also known as: SFD, System Dynamics Model
Diagram modeling system behavior via stocks, flows, and connectors to visualize accumulation and rates of change.
DESCRIPTION
A stock-flow diagram represents a system using stocks (levels), flows (rates), and information links. The formal notation includes reservoirs, pipes, and valves to encode dynamics. These diagrams enable simulation and policy analysis for complex systems. They differ from causal loop diagrams by quantifying accumulations and rates. Tools like Vensim and Stella facilitate building, validating, and experimenting with models.
ALTERNATIVE DEFINITIONS
Wikipedia
Diagrams of stocks and flows are used to model dynamic systems where stocks represent accumulations and flows represent rates of change.
Connects the diagrammatic approach directly to dynamic system modeling.
Vensim Documentation
Stock and flow diagrams use a formal notation to represent accumulations (stocks) and rates (flows) for constructing simulation models.
Emphasizes formal notation for building runnable simulations.
RELATED TERMS
Stock Flow Feedback Loop System Dynamics Simulation Model Vensim Stella Differential Equation Policy Design
COMPETING TERMS
KNOWLEDGE AREAS
Mathematics Domain & Business Context Data Science
TARGET AUDIENCE
Data Scientist Enterprise Architect Digital Transformation Manager Data Strategy Consultant
EXTERNAL SOURCES
- Wikipedia - Stock and flow
- Vensim - Documentation for stock-flow modeling
- isee systems - Tooling for stock-flow diagrams
- System Dynamics Society - Resources on system dynamics modeling
TOP QUESTIONS
Why use a Stock-Flow Diagram instead of a Causal Loop Diagram?
Stock-flow diagrams quantify accumulations and rates, enabling simulation. Causal loops show qualitative feedback without explicit quantities.
Category: Misunderstanding
What elements make up a Stock-Flow Diagram?
Stocks, flows, valves, sources/sinks, and information links. Units and equations define behavior.
Category: Overview
How do Stock-Flow Diagrams support policy testing?
They simulate interventions and feedback effects over time. Analysts compare trajectories and outcomes under different policies.
Category: Example
What are common modeling mistakes in Stock-Flow Diagrams?
Inconsistent units, missing delays, and unbalanced flows. Over-simplification hides important dynamics.
Category: Mistakes
How to validate a Stock-Flow Diagram?
Check conservation laws, unit consistency, and sensitivity. Compare outputs to historical data and expert expectations.
Category: Testing
What risks exist when interpreting simulation results?
Overconfidence in model assumptions and parameters. Misinterpretation can misguide decisions.
Category: Risk
Which tools are popular for Stock-Flow modeling?
Vensim, Stella Architect, and Insight Maker. They provide diagramming, simulation, and calibration features.
Category: Overview
Can Stock-Flow Diagrams represent non-linear dynamics?
Yes, through equations defining flows and feedback. Thresholds and saturation create non-linear behaviors.
Category: Opinion
Where to start learning Stock-Flow modeling?
Begin with introductory tutorials and model simple reservoirs. Gradually add feedback loops and realistic parameters.
Category: Getting-Started