Definition
A Causal Loop Diagram (CLD) is a visual tool used in System Dynamics to represent the feedback structure of a complex system. It maps how various system variables relate to one another through cause-and-effect links.
Why It Matters
They reveal the hidden feedback structures that cause systems to behave in non-intuitive ways, allowing for more effective interventions in complex problems.
Core Concepts
- Links: Represented by arrows connecting an independent variable to a dependent one.
- Polarity:
- Positive (+): A change in the first variable causes a change in the same direction in the second (e.g., more births more population).
- How to read: “The births lead to population, which indicates a positive polarity.”
- Meaning: A positive link—change in the first variable causes change in the same direction in the second (both up or both down).
- Negative (-): A change in the first variable causes a change in the opposite direction (e.g., more deaths less population).
- How to read: “The deaths lead to population, which indicates a negative polarity.”
- Meaning: A negative link—change in the first variable causes change in the opposite direction in the second.
- Positive (+): A change in the first variable causes a change in the same direction in the second (e.g., more births more population).
- Feedback Loops:
- Reinforcing Loop (R / +): An even number of negative links (or all positive) that leads to self-amplifying growth or decay.
- Balancing Loop (B / -): An odd number of negative links that resists change and seeks stability.
- Delay: Represented by hash marks on a link, indicating that the effect takes time to manifest.