Introduction to System Dynamics


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This is the introduction presentation on Systems Dynamics based from materials of Jay Forrester and John Sterman

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Introduction to System Dynamics

  1. 1. System Dynamics Understanding system behavior by identifying system structure
  2. 2. Some Phrases to Ponder.. <ul><li>Experience is an expensive school – Benjamin Franklin </li></ul><ul><li>Experience is something you get after you need it – anon </li></ul>
  3. 3. What is a System? <ul><li>A collection of parts organized for a purpose . </li></ul>
  4. 4. Why does a System Fail? <ul><li>It fails to achieve its purpose. </li></ul><ul><li>The parts are poorly designed or poorly connected. </li></ul><ul><li>It is knocked off course because of external shock. </li></ul><ul><li>It is inherently incapable of meeting its purpose or it attempts to adjust to changes. </li></ul><ul><li>Its policies are badly designed. </li></ul>
  5. 5. Linear Thinking of Events
  6. 6. Dynamic Behavior of a System
  7. 7. Critical Elements in a Dynamic Behavior <ul><li>Delay - time lags or reaction time of the decision with respect to its effect on the system </li></ul><ul><li>Amplification - when an action turned out to be more forceful than what it was intended </li></ul>
  8. 8. History of SD <ul><li>System Dynamics was originally developed in the 1950's and 1960's at MIT by Jay Forrester </li></ul><ul><li>An Electrical Engineer who invented the random-access magnetic core memory in digital computers. </li></ul><ul><li>Applied his background in computer sciences and engineering to the development of computer modeling and analysis of social systems. </li></ul><ul><li>The SD methodology was based on ideas of feedback, such as encountered in electrical and mechanical control systems. </li></ul>
  9. 9. History of SD <ul><li>He was also the founder of MIT System Dynamics group. He directed the System Dynamics Program in the Sloan School until 1989 </li></ul><ul><li>SD was developed to evaluate how alternative policies affect growth, stability, fluctuation, and changing behavior in corporations, cities, and countries. </li></ul><ul><li> </li></ul>
  10. 10. What is System Dynamics <ul><li>It is the investigation of information-feedback characteristics of managed systems. </li></ul><ul><li>The use of models for the design of improved organizational form and guiding policy. </li></ul><ul><li>- Jay Forrester (Founder of SD) </li></ul>
  11. 11. What is System Dynamics (SD)? <ul><li>Deals with the time-dependent behavior of managed systems. </li></ul><ul><li>Aims to describe the system and understand it. (Focuses on patterns of behavior not on events). </li></ul><ul><li>Apply qualitative and quantitative models on how information feedback govern its behavior. </li></ul><ul><li>Designing robust information feedback structures and control policies through simulation and optimization. </li></ul>
  12. 12. SD Approach by R.G. Coyle <ul><li>Problem recognition </li></ul><ul><li>Problem understanding and system description </li></ul><ul><li>Qualitative analysis </li></ul><ul><li>Simulation modeling and testing </li></ul><ul><li>Policy design and testing </li></ul>
  13. 13. SD Approach by Richardson and Pugh <ul><li>Problem identification and definition </li></ul><ul><li>System conceptualization </li></ul><ul><li>Model formulation </li></ul><ul><li>Analysis of model behavior </li></ul><ul><li>Model evaluation </li></ul><ul><li>Policy analysis </li></ul><ul><li>Model use or implementation </li></ul>
  14. 14. Characteristics of a Messy Problems (Or why are problems messy?) <ul><li>Dynamic – “all is change” </li></ul><ul><li>Tightly coupled – “you can’t do just one thing” </li></ul><ul><li>Governed by feedback – “our decisions alter the state of the world” </li></ul><ul><li>Nonlinear – “effects are rarely proportional” </li></ul><ul><li>History-dependent – “you cannot unscramble you eggs” </li></ul>
  15. 15. Characteristics of a Messy Problems (Or why are problems messy) <ul><li>Self organizing – “dynamics arise from internal structure” </li></ul><ul><li>Adaptive – “people change over time” </li></ul><ul><li>Counterintuitive – “too focused on symptoms of difficulty rather than the underlying cause” </li></ul><ul><li>Policy resistant – “many obvious solutions fail or worsen the situation” </li></ul><ul><li>Characterized by trade-off – “high leverage policies cause worst to better behavior, while low leverage policies result to temporary improvement before getting worse” </li></ul>
  16. 16. Elements of a Dynamic Problem <ul><li>Dynamic behavior of important variables – identify and graph those variables in the system that are the symptoms of the problems we wish to study. </li></ul><ul><li>Time horizon – period of time over which the problem plays itself out. </li></ul>
  17. 17. Elements of a Dynamic Problem <ul><li>The reference behavior mode – patterns over time that will be referred to again and again. </li></ul><ul><li>Thinking in terms of graphs over time – looking for long-term dynamic consequences. Use graphs to describe, define, and analyze a problem. </li></ul>
  18. 18. Example of a problem statement <ul><li>There is a an exponential growth of people in Metro Manila from 1900 – 2000 which can lead to urban decay. </li></ul><ul><li>There is a recurring pattern on the occurrence of Dengue Fever among young children (1 to 10 years old) in Tondo between 1990 to 2000 which led to child deaths. </li></ul>
  19. 19. Barriers to Learning <ul><li>Dynamic complexity </li></ul><ul><li>Limited information </li></ul><ul><li>Confounding variables and ambiguity </li></ul><ul><li>Bounded rationality and the misperceptions of feedback </li></ul><ul><li>Flawed cognitive map </li></ul><ul><li>Erroneous inferences about dynamics </li></ul><ul><li>Unjustified reasoning (judgmental errors and bias) </li></ul><ul><li>Defensive routines and interpersonal impediments to to learning </li></ul><ul><li>Implementation failure </li></ul>
  20. 20. Watson Card Puzzle <ul><li>You are shown 4 cards. Each card has a letter on one side and a number on the other side. What is the smallest number of cards you should turn over to test the rule that cards with vowels on one side have even numbers on the reverse? Which are they? </li></ul>
  21. 21. Watson Card Puzzle E 4 7 K
  22. 22. Questions <ul><li>What are the important symptom variables? </li></ul><ul><li>What is the time horizon of your problem? </li></ul><ul><li>What reference behavior mode you expect to see? (What is, what should, what you think is, what could) </li></ul><ul><li>What are the long term dynamic consequences of the problem? </li></ul>
  23. 23. Group work <ul><li>Identify the problem by answering its 4 elements. </li></ul><ul><li>Construction of government projects. </li></ul><ul><li>Population of the Philippines. </li></ul><ul><li>Traffic congestion in Edsa. </li></ul><ul><li>Garbage collection in Baclaran market. </li></ul><ul><li>Corruption in the government. </li></ul>
  24. 24. Group work <ul><li>Identify the problem by answering its 4 elements. </li></ul><ul><li>Dieting </li></ul><ul><li>Addiction </li></ul><ul><li>Population of the World </li></ul><ul><li>Use of Credit Card </li></ul><ul><li>Salary/Wage Increase </li></ul>
  25. 25. Individual Work <ul><li>Electricity </li></ul><ul><li>Cum GPA </li></ul><ul><li>National Population </li></ul><ul><li>Imported product </li></ul>