Causal loop diagram
A diagram of words and arrows that shows how variables influence each other and which loops reinforce or balance a system.
What it’s for
It helps you see why a problem keeps coming back or gets worse, and where to intervene to change it.
Key elements
Every arrow, a sign
With “+” both variables move in the same direction; with “−”, in opposite directions.
Loops that reinforce or balance
Some amplify a change, like a vicious circle; others slow it toward a limit.
Delays matter
An effect that takes time to arrive explains many swings; mark it on the arrow.
How it’s done
Name the variables as things that can go up or down.
Connect them with arrows and mark whether each relationship adds or subtracts.
Look for the loops and tell the story they explain.
Applications in design
When to use it
When a problem keeps coming back and quick fixes don’t solve it.
Avoid
Adding so many variables that nobody can follow it.
Don’t fall for it
It’s an explanation to be checked against data and against the people in the system.
Connections
Builds on
Authors and works
- 1963
Magoroh Maruyama
Described self-amplifying causal processes; according to the field’s history, it is the first published use of a diagram of this kind.
- 2000
John D. Sterman
Explained how to draw and read them within system dynamics; the exact origin of the method is debated.
Sources
Original sources
- Maruyama, M. (1963). The second cybernetics: Deviation-amplifying mutual causal processes. American Scientist, 51(2), 164–179.
Secondary sources
- Sterman, J. D. (2000). Business dynamics: Systems thinking and modeling for a complex world. Irwin/McGraw-Hill.
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