Endogenous Variable - PowerPoint Presentation

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 Slide9
Slide10

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. Slide11
Slide12
Slide13

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.