Formulating a Dynamic Hypothesis Once the problem has been identified and characterized over an appropriate time modeler must develop a theory called dynamic hypothesis that accounts for the problematic behavior ID: 274635
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Slide1
Endogenous VariableSlide2
Formulating a Dynamic
Hypothesis
Once the problem has been identified and
characterized
over an appropriate time, modeler must develop a theory called “
dynamic hypothesis
” that accounts for the problematic behavior.
It is dynamic because it provides an explanation of the dynamics characterizing the problem in terms of the underlying feedback and stock and flow structure of the system.
A dynamic hypothesis is a working theory of how the problem arose.
Theory development often happens in a team of clients.
But, system dynamics seeks
endogenous explanations
for phenomena.Slide3
Endogenous= arise from within
An endogenous theory generates the dynamic of a system through the interaction of the variables and agents represented in the model.
By specifying how the system is structured and the rules of interaction (the decision rules in the system), you can explore the patterns of behavior created by those rules and that structure .
Exogenous (arise from without ) explanation
, explains the dynamics of variable in terms of other variables whose behavior you have assumed.
Is system dynamics blind to exogenous variables?Slide4
An Example
Exogenous point of view
Sam is always mean to Pam.
It
’s all his fault.If he would be nicer, Pam’s life would be better.
Endogenous point of viewMaybe there is something Pam is doing …Slide5
Feedback Loops are a Consequence of the Endogenous Point of ViewSlide6
Expanding the Boundary to Enable
an Endogenous Point of ViewSlide7
Endogeneity and Feedback
Feedback loops enable the endogenous point of view and give it structure.
[Richardson 1991]Slide8
Mapping
S
ystem Structure
System dynamics includes a variety of tools to communicate the boundary of your model and represent its casual structure.
Model boundary chart: it summarizes the scope of model by listing which key variables are included endogenously, which are exogenous and which are excluded from the model.Usefulness: they are tools of inquiry but not weapons in a war of advocacy.
Example: feedbacks between energy system and economy Slide9Slide10
Subsystem
diagram
It is the overall architecture of a model. Each major subsystem is shown along with the flows of material, money, goods, information, and so on coupling the subsystems to one another.
Subsystem diagrams convey information on the boundary and level of aggregation in the model by showing the number and type of different organizations or agents represented. Slide11Slide12Slide13
Examples
Global Warming
Flood Damage
TerrorismSlide14
The Global Warming Debate
Exogenous view:
We are in the warm phase of a 100,000 year cycle caused by exogenous, structural characteristics
Policy implication: Adapt to the inevitable
Endogenous view: Human activity is exacerbating the natural cyclePolicy implication: Alter human habits to minimize the coming tragediesSlide15
Both perspectives involve stock-and-flow / feedback dynamics
The water cycle
The carbon cycle
Heat trapping
Water vapor
Atmospheric CO2
Other GH gases
Cloud cover
Heat reflecting- Ice albedo- Cloud albedo- AerosolsSlide16
Both may even acknowledge reinforcing feedback loops
Water vapor
Cloud cover
Ice albedoSlide17
Terrorism
Exogenous view:
Violent forces exist that threaten others, and they are growing.
Policy implication: Defend to prevent harm; attack to weaken or eliminate the violent forces.
Endogenous view: Violent forces interact with defenses and attacks to create the rising tensions we observe.
Policy implication: Defend to prevent harm; minimize behaviors that create nasty reinforcing loops; maximize creation of beneficial reinforcing loops; work toward cross-cultural understandings.Slide18
Largely Exogenous Views of Terrorism
(various internet sources; see paper)
Ethnicity
, nationalism/separatism, poverty and economic disadvantage, globalization, (non)democracy, Western society, disaffected intelligentsia, dehumanization, and religion
Marginalization, ethnicity and nationalism, religion, cultism, free flow of weapons, training of non-military personnel, no pure democracy present
Belief causes terrorism. Foreign domination and control of Muslim resources, the hatred of the Western way of life. alienation. poverty and illiteracy. moral decadence of the West. the West's support for Israel.
Economic deprivations, political injustices, foreign occupation and denial of fundamental rights including the right to self-determinationSlide19
Endogenous View of
Structure and Dynamics of Terrorist Cells
New recruits
Terrorist group
Losses
Terrorist actions
Suppression activities
Zeal
Peripheral support
Funding
Martyrs to the cause
(R)
(R)
(B)
(R)
(R)
(R)
(B)
(R)
(R)Slide20
Flood Damage
Exogenous view:
Floods happen sometimes; the greater the flood, the worse the damage.
Policy implication: When floods happen to occur, recover and rebuild.
Endogenous view: Damage occurs when hazard meets vulnerability; vulnerability is a result of people policiesPolicy implication: Recognize human role in damage. Work with stakeholders to minimize vulnerabilities. Slide21
An Exogenous View of Flood Damage
Flood severity
Flood frequency
Structural mitigation policies
Flood damageSlide22
A Model of Floods in which
Identical Floods Do Not Cause Identical DamageSlide23
Underlying Causes of Damage:
Evolution of Land Use and Natural BarriersSlide24
An Endogenous View of Flood DamageSlide25
Referensi
Morasae
, E.K. 2012. Formulating dynamics hypothesis.
Center
for Community-Based Participatory Research in Health. Tehran University of Medical SciencesSterman, J.D. 2000. Business dynamics. Irwin-MGH.