Lecture notes

Question 1

What does it mean to analyse a problem with an endogenous focus?

Answer 1

Analyzing a problem with an endogenous focus means examining how internal factors within the system itself generate and sustain the problem, rather than looking for external causes.

Question 2

What is dynamics?

Answer 2

In system dynamics, “dynamics” refers to the behavior and evolution of a system over time, driven by feedback loops, interactions, and changes within the system’s structure.

Question 3

What is meant by “The enemy is not out there”?

Answer 3

In system dynamics, “the enemy is not out there” means that problems often stem from within the system itself, not from external forces. It emphasizes the need to focus on internal feedback loops and decision-making processes rather than blaming outside factors.

Question 4

What is a system?

Answer 4

A system is a collection of interconnected components that work together to achieve a specific purpose, where the behavior of the whole depends on the interactions between its parts.

Question 5

What is a model of a sytem?

Answer 5

A model of a system is a simplified representation that captures the key components and interactions within a system, used to analyze, understand, and predict the system’s behavior.

Question 6

What is the distinction between structure and behaviour in a system or a model?

Answer 6

In a system or model, structure refers to the arrangement and relationships between components, while behavior refers to how the system evolves and responds over time due to its structure. Structure determines behavior.

Question 7

How does one assess if change is closely associated with the operation of the internal strucutre of the internal structure of an identifiable system?

Answer 7

*Is it a dynamic management problem? Are “managers” needed?
* Are there identifiable interacting system components?
* Is the problem recurrent and chronic, repeating itself over time and space?
* Can it trivially and appropriately be explained by some factors from the outside?

Question 8

What is the System Dynamics Approach?

Answer 8

Analysis of dynamic problems
with an endogenous focus.

The system dynamics approach is a method for understanding and analyzing complex systems by modeling their structure, feedback loops, and time delays to study how these elements influence the system’s behavior over time.

Question 9

What is system dynamics modeling?

Answer 9

System dynamics modeling is the process of creating a simulation model to represent and analyze the interactions, feedback loops, and time delays within a system to understand its behavior and predict future outcomes.

Question 10

What characterized dynamics and dynamic problems?

Answer 10

Dynamics and dynamic problems are characterized by change over time, driven by feedback loops, time delays, and the complex interactions within a system. These problems evolve and are influenced by the system’s structure and internal processes.

Question 11

What is boundary selection in system dynamics?

Answer 11

Boundary selection is the process of defining the scope of a system by deciding which elements and interactions are included or excluded, shaping the focus and outcomes of the analysis.

Question 12

What is the distinction between physical models and symbolic models? Give an example of each.

Answer 12

Physical models are tangible representations of a system, like scale models or prototypes, that mimic the physical properties of the system. Symbolic models use abstract symbols, such as equations, diagrams, or simulations, to represent the system’s behavior and structure.

Physical model example: A scale model of a bridge, which is a tangible, smaller representation used to study the structural properties and behavior of the bridge.

Symbolic model example: A mathematical equation representing the relationship between supply and demand in economics, using symbols and variables to describe how the system behaves.

Question 13

What is the distinction between static models and dynamic models? Give one example of each.

Answer 13

Static models represent a system at a specific point in time, focusing on structure without considering changes over time. Dynamic models capture how a system evolves, showing changes and interactions over time.

Static model example: A floor plan of a building, which shows the layout at a single point in time without considering any changes or movements.

Dynamic model example: A weather forecast simulation, which models how weather conditions change over time, predicting future states based on current data.

Question 14

What is the distinction between descriptive models and a prescriptive model?

Give an example of both.

Answer 14

Descriptive models explain or represent how a system works or behaves, focusing on understanding and analyzing current or past states. Prescriptive models provide recommendations or guidelines on how to achieve desired outcomes, focusing on guiding decisions and actions.

Descriptive model example: A demographic study that analyzes population trends over the past decade, showing how birth rates and migration patterns have shaped the current population.

Prescriptive model example: An optimization model for supply chain management that recommends the most efficient routes and inventory levels to minimize costs and meet demand.

Question 15

What is the distinction between time continuous models and discrete models? Give an example of each.

Answer 15

Time continuous models represent systems where changes occur smoothly over time, with variables evolving continuously. Discrete models represent systems where changes occur at specific intervals or steps, with variables updating at distinct points in time.

Time continuous model example: The cooling of a hot object modeled by Newton’s Law of Cooling, where the temperature change is represented as a continuous process over time.

Discrete model example: A population growth model using a yearly census, where population numbers are updated at discrete intervals (e.g., every year).

Question 16

What are some categories of basic dynamic behaviour patterns typically seen in systemic feedback problems?

Answer 16

Exponential Growth: A reinforcing feedback loop where a system variable increases at an accelerating rate over time.

Exponential Decay: A balancing feedback loop where a system variable decreases at a decreasing rate, eventually stabilizing or reaching zero.

S-Shaped Growth: Growth that starts exponentially but slows down as limits or constraints are reached, often due to balancing feedback, leading to a stable equilibrium.

Oscillation: Repeated cycles of rising and falling values, often caused by delays in feedback loops, where the system fluctuates around an equilibrium point.

Overshoot and Collapse: Rapid growth followed by a sudden decline or collapse when the system exceeds its carrying capacity or limits.

Stable Equilibrium: A pattern where the system stabilizes at a certain level due to balancing feedback, with minimal fluctuation.

Shifting Dominance: A situation where the behavior of a system changes over time as different feedback loops become dominant, altering the system’s trajectory.

Question 17

What is exponential growth?

Answer 17

Exponential growth is a dynamic behavior pattern where a quantity increases at an accelerating rate over time, typically due to a reinforcing feedback loop. This type of growth can be observed in populations, investments with compound interest, or the spread of a viral infection, where the rate of increase is proportional to the current size, leading to rapid expansion.

Question 18

What is exponential decay?

Answer 18

Exponential decay is a dynamic behavior pattern where a quantity decreases at a decreasing rate over time, typically due to a balancing feedback loop. Examples include the cooling of a hot object, radioactive decay, or the depletion of a resource, where the rate of decline slows as the quantity diminishes, eventually approaching zero or a stable level.

Question 19

S-Shaped Growth

Answer 19

S-shaped growth is a dynamic behavior pattern where a system initially experiences rapid, exponential growth, but as it approaches certain limits or constraints, the growth rate slows down, eventually stabilizing at a maximum level. This pattern is often seen in populations, resource usage, or the adoption of new technologies, where the growth accelerates initially but then levels off as factors such as resource limitations, market saturation, or increased competition come into play. The resulting curve resembles the shape of an “S.”

Question 20

What is Oscillation?

Answer 20

Oscillation is a dynamic behavior pattern where a system exhibits repeated cycles of rising and falling values over time, typically around an equilibrium point. This pattern occurs due to delays in feedback loops where the system overcorrects in response to changes, leading to continuous fluctuations. Examples include the swinging of a pendulum, economic cycles of boom and bust, or predator-prey population dynamics in ecology. The system alternates between phases of growth and decline, often with regular periodicity.

Question 21

What is overshoot and collapse?

Answer 21

Overshoot and collapse is a dynamic behavior pattern where a system initially experiences rapid growth, exceeding its sustainable limits or carrying capacity, leading to a subsequent sharp decline or collapse. This occurs when resources are depleted, constraints are breached, or the system can no longer support its expanded state. Examples include environmental degradation where a population exceeds the ecosystem’s capacity, or economic bubbles that burst after unsustainable growth. The system grows rapidly but then crashes when it can no longer sustain the excessive demands placed on it.

Question 22

What is Stable Equilibrium?

Answer 22

Stable equilibrium is a dynamic behavior pattern where a system settles into a steady state and remains at a constant level over time, despite small disturbances. In this state, any minor deviation from the equilibrium triggers balancing feedback mechanisms that bring the system back to its stable condition. Examples include a pendulum at rest, a balanced market supply and demand, or a population that has reached its carrying capacity. In stable equilibrium, the system resists change and tends to return to its equilibrium point after being disturbed.

Question 23

What is shifting dominance?

Answer 23

Shifting dominance is a dynamic behavior pattern in systems where the influence of different feedback loops changes over time, leading to alterations in the system’s behavior. Initially, one feedback loop may dominate, driving the system in a particular direction, but as conditions evolve, another feedback loop becomes more influential, causing a shift in the system’s trajectory. This pattern can lead to changes in growth rates, oscillations, or transitions from stability to instability. An example is an economy that shifts from growth driven by consumer demand to one constrained by resource shortages, changing the system’s overall behavior.