Principle
Separate stock from flow
Stocks remember history; flows change stocks.
When it fits
- When a system has accumulation, backlog, inventory, skill, debt or another quantity that changes over time.
When to avoid it
- A causal map is a hypothesis, not proof. Keep evidence, time scale, boundary choices and alternative explanations visible before acting on a loop.
Why it matters
Identify what accumulates and which inflows or outflows alter it. This prevents treating a large backlog as if it were only today's arrival rate.
An example
Unresolved defects are a stock; new defects and reopens are inflows, verified fixes are an outflow.
Check your result
The map distinguishes accumulated quantity from rates that change it.
Keep this limit in mind
- A causal map is a hypothesis, not proof. Keep evidence, time scale, boundary choices and alternative explanations visible before acting on a loop.
Connected ideas
Useful withMap the reinforcing loop behind growth
Evidence and sources
Supports
System dynamics work emphasizes that well-intended interventions can be defeated by feedback-driven system responses, a pattern described as policy resistance.
A qualitative feedback story is not enough; links, delays and predicted behavior still need empirical or operational checking.
System Dynamics Modeling: Tools for Learning in a Complex World · Abstract