public policy modeling causal loop diagrams saturday, september 05, 2015 hun myoung park, ph.d....

Public Policy Modeling

Causal Loop Diagrams Wednesday, April 19, 2023

Hun Myoung Park, Ph.D.

Public Management & Policy Analysis ProgramGraduate School of International Relations

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Causal Loop Diagram 1

• A CLD or causal map depicts the structure of a system or a set of causal relationships among variables (activities) in a system

• Used in system dynamics

• But general tool to describe concepts (systems) and communicate with others

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Causal Loop Diagram 2

• CLD consists of – Variables of a system. Interdependent (→V

→), dependent (→V), and independent (V→)– Cause-and-effect relationships among

variables, “S” for the same direction or “O” for the opposite direction

– Feedback loop is a closed circuit of interconnection between variables. “R” for reinforcing feedback or “B” for balancing

– Delay

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Drawing a CLD 1

1. Identify a systemic problem that is chronic and recurring and has a history and/or pattern.

2. Set a boundary and level of simplicity

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Drawing a CLD 2

3. Identify key variables (activities) that are significant events or phenomena that jointly influence the overall system.

– Use nouns or noun phrases– Include “the level of,” “the amount of,”

“the number of,” or “the size of,” if possible.

– Use a neutral or positive term. Avoid such words as “failure” and “increase.”

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Drawing a CLD 3

4. Begin with more interesting variable (activity) and work backward (begin with an effect and look for its cause) or move back and forth (both directions).

5. Indicate “cause-and-effect” relationship (direction of relationships) using a link and arrow. A departing point influences the destination (A→B).

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Drawing a CLD 4

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Drawing a CLD 5

6. Indicate the type of the relationship between two variables on the link.

• + or S (same direction) means a positive relationship between two variables. When A increases, B will increases; When A decreases, B will decreases.

• - or O (opposite direction) indicates a negative relationship. If A increases, B will decrease; when A decreases, B will increase.

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Drawing a CLD 6

7. Delay means that it takes long time for an cause results in its effect.

– Depicted by || or “Delay” on the link– “[M]ake system’s behavior unpredictable

and confound our efforts to control that behavior.” (Anderson & Johnson,1997, p.57)

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Drawing a CLD 7

8. If a link between two variables is not clear, redefine the variables or insert an intermediate variable between the two.

9. Keep revising iteratively; No CLD is ever finished. Begin with a simple CLD and try more challenging one incrementally.

10. Label feedback loop with either “R” for reinforcing or “B” for balancing

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An Example of CLD 1

• “Work backward” begins with the important effect and then seeks subsequent cause-effect chains.

• “Begin at the beginning” or work forward

• “Go back and forth”

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An Example of CLD 1

• Bank failure as a system problem• First ask, “What caused the bank failure?” • Probably “bank’s solvency” is the cause of

“bankruptcy (bank failure).”• What is the relationship between the two

variables? When bank’s solvency is low, bank failure is more likely (high). – or O

• Then ask, “What caused bank’s solvency?” Probably…

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An Example of CLD 3

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An Example of CLD 4

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Software for CLD

• Vensim (https://vensim.com/)

• iThink (http://www.iseesystems.com/)

• STELLA (http://www.iseesystems.com/)

• Powersim (http://www.powersim.com/)

• Anylogic (http://www.anylogic.com/)

• You may also try LibreOffice Draw or Microsoft Visio

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Feedback Loop 1

• A feedback loop is a closed circle of interconnection between variables or a series of mutual cause and effect (causal relationships).

• The loop is internally initiated by the system and insensitive to environment.

• Mutual causation is the simplest feedback loop. A→B→A→B→…

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Feedback Loop 2

• Initial cause and ultimate consequence is NOT distinguishable clearly.

• “[E]verything is indeed connected to everything else, so, in principle, it doesn’t matter where you start” (Sherwood, 2002: 128).

• “[C]ycling back means that what was originally a cause is now suddenly an effect” (Weick, 1979: 77).

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Feedback Loop 3

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Feedback Loop 4

• “[A]ny change made anywhere will eventually itself be changed by the consequences it triggers” (Weick, 1979: 77)

• Given endless cause-effect chains, such distinction is almost meaningless in most circumstance.

• The interdependent relationships in a structure (system) are more important.

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Reinforcing Feedback Loop 1

• A reinforcing or positive feedback loop

• A feedback loop with even number of negative signs (-) or O (i.e., 0, 2, 4, …).

• Depicted by “R” or “+” in the center of a feedback loop

• Self-reinforcing feedback or deviation amplifying feedback.

• No regulation or control

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Reinforcing Feedback Loop 2

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Reinforcing Feedback Loop 3

• “Reinforcing loops can be seen as the engines of growth and collapse” (Anderson & Johnson, 1997: 54).

• Destabilize the system and deviate from its equilibrium

• Form a vicious circle or virtual circle

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Balancing Feedback Loop 1

• A balancing or negative feedback loop• A feedback loop with odd number of

negative sign (-) or O (i.e., 1, 3, 5, …).• Depicted by “B” or “-” in the center• Goal seeking feedback, stabilizing

feedback, deviation-counteracting, or self-refraining feedback

• Since circulation of feedback loop will produce balance or equilibrium.

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Balancing Feedback Loop 2

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Multiple Feedback Loop 1

• What if there are multiple feedback loops in a system? Some loops are balancing, while others are reinforcing

• If “loops are of unequal importance,” then which feedback loop is dominating in the system?

• Such dominating or the most important loop will determine the fate of the system in the end (Weick, 1979: 74).

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Multiple Feedback Loop 2

• “[T]he greater the number of inputs to and/or outputs from an element, the more important that element is” (Weick, 1979: 75).

• “[C]lose loop that contains the greatest number of these important elements” (Weick, 1979: 75-76)

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Multiple Feedback Loop 3

• In case of equal importance• Count the number of negative loops• Count the total number of negative

relationships (count whenever it appears in a feedback loop)

• An odd number indicates a balancing or deviation-counteracting system

• An even number indicates deviation-amplifying system (Weick, 1979: 76).

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Change in a System

• How to change a system?– Change in a relationship from – (opposite) to

+ (same direction) – Change in a relationship from – (same) to -

(opposite direction)– Add some relationships– Delete relationships– Shock (external input) will be decayed

without changing the structure of a system

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Impact of DDT on Malaria 1

DDT UseDisease (Malaria)

Mosquito

S

O

S

B1

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Impact of DDT on Malaria 2

DDT UseDisease (Malaria)

Mosquito

S

O

SB1

DDT in Breast Milk

S

S

R2

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Impact of DDT on Malaria 3

DDT UseDisease (Malaria)

Mosquito

S

O

SB1

DDT in Breast Milk

S

S

R2

DDT Accumulation inGecko (Lizard)

# Cat

# Rat

S

OO

S

R3

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http://butane.chem.uiuc.edu/pshapley/Environmental/L37/1.html

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Impact of DDT on Malaria 4

DDT UseDisease (Malaria)

Mosquito

S

O

SB1

DDT in Breast Milk

S

S

R2

DDT Accumulation inGecko (Lizard)

# Cat

# Rat

S

OO

S

R3

# Parasitic Wasp

# Caterpillar

# Thatch Roof Eatenand Destroyed

O

O

S

S

S

R4R5

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Impact of DDT on Malaria 4

• Loop 1 (Balancing): DDT Use→Mosquito →Disease

• Loop 2 (Reinforcing): DDT Use→DDT in Breast Milk→Disease

• Loop 3 (Reinforcing): DDT Use→DDT in Gecko→Cat→Rat→Disease

• Loop 4 (Reinforcing): DDT Use→Wasp →Caterpillar→Thatch Roof→Disease

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Economy and Population 1

• Sherwood (2002, pp.241-262)

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Economy and Population 2

• Sherwood (2002, pp.241-262)

Deaths

Population

Births

Death Rate

Birth Rate

O

S

S

S

S

S

R2

B1

Disease

S

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Economy and Population 3

• Sherwood (2002, pp.241-262)

Deaths

Population

Births

Death Rate

Birth Rate

O

S

S

S

S

S

R2

B1

Disease

S

Economic Activity

Desire for Wealth

S

S

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Economy and Population 4

• Sherwood (2002, pp.241-262)

Deaths

Population

Births

Death Rate

Birth Rate

O

S

S

S

S

S

R2

B1

Disease

S

Economic Activity

Desire for Wealth

S

S

Resource Consumption

Pollution

S

S

S

B3

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Economy and Population 5

• Sherwood (2002, pp.241-262)

Deaths

Population

Births

Death Rate

Birth Rate

O

S

S

S

S

S

R2

B1

Disease

S

Economic Activity

Desire for Wealth

S

S

Resource Consumption

Pollution

S

S

S

B3

Competition forScarce Resources

Resource Capacity

Famine

War

O

SS

SS

S

B5

B4

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Economy and Population 6

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Economy and Population 7

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Common Pool Resources

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Corruption System