Daniel Aronson, Stocks and Flows: Converting From Causal Loop Diagrams.

Daniel Aronson, “Step-By-Step Stocks and Flows: Converting From Causal Loop Diagrams,” January 17, 2016, https://thesystemsthinker.com/step-by-step-stocks-and-flows-converting-from-causal-loop-diagrams/.

Reading notes.

To convert Causal Loop Diagrams to Stock and Flow diagrams:

1. Identify the units used for each variable in the CLD. Makes the diagram more precise, starts identifying where time is a variable (therefore insinuating a flow), and points out missing variables.
2. Identify stocks. The prior step may have noted flows, which indicate stocks. (Note that not all time-involved variables are definitely flows.) Consider whether there are additional stocks to involve. (Stocks are drawn as rectangles)
3. Identify flows. What increases a stock? Decreases it? Every one of these processes is a flow. (Flows are drawn as fat arrows with a circle indicating the activity with a valve connected to it)
4. Connect stocks and flows. All decreasers are outflows, all increasers are inflows. A stock may need to be connected to a flow if the stock’s size provides information to modulate the flow—information links are line arrows.
5. Add and link remaining variables. Anything left over is either a constant (like market size) or a calculation (like % market untapped). These variables can only influence each other and flows. If it seems like they are influencing a stock, then they might actually be a full-on flow and should be reconsidered. Variables are just circles connected by information arrows.
6. Check units. Make sure they all line up and use the same time increments.
7. Add any remaining variables. The goal here is to get to a calculable model, so any missing ratios etc need to be added to get there.