Book Summary: Thinking in Systems

Let’s say you want to build the perfect self-driving vehicle. This thing you want to make is composed of many parts. There’s the car itself made up of many subparts (engine, tires, transmission, etc) as well as the AI tech. Realistically you will need a bunch of speciallized embedded systems as well as a central computer to orchestrate everything. There’s sensors, actuators, orchestrators, etc. In short, how does one person know if a design is good? How do you know how fast the visual recognition needs to be to handle controlling a car going 60 mph?

It turns out that complexity can make or break your design. This book offers a mental model you can use to create abstractions that make reasoning about complex phenomena easier: The system. It turns out you can model a lot of natural and artificial systems by thinking about Stocks, Flows and Dynamic Equilibrium.

This tool will help you analyze complex systems to find bottlenecks. It helps you reason about the trade-offs in the design. You can use the system domain to communicate the behaviour and structure of your system using a shared language.

I took these notes while reading the book

Summary of System Principles

System

  • A system is more than the sum of its parts
  • Many interconnections work through the flow of information
  • The least obvious parts of the system, its function or purpose, is often the most crucial determinant of the system’s behavior
  • System structure is the source of system behavior. System behavior reveals itself as a series of events over time.

Stocks, Flows and Dynamic Equilibrium

  • A stock is the memory of the history of changing flows within the system
  • If the sum of inflows exceeds the sum of outflows, the stock level will rise
  • If the sum of outflows exceeds the sum of inflows, the stock level will fall
  • Stock levels stay the same when there is dynamic equilibrium. The stock inflows are equat to the stock outflows
  • Stock can be increased two ways, decrease its output flow or increase its input flow
  • Stocks act as delays or buffers or shock absorvers in systems
  • Stocks allow inflows and outflows to be decoupled and independent

Feedback Loops

  • Balancing feedback loops are equilibrating. They provide stability of resistance to change
  • Reinforcing feedback loops are self-enhancing. It can give you exponential growth or runaway collapse

Shifting Dominance, Delays and Oscillations

  • Delays in feedback makes oscillations

Scenarios and Testing Models

  • System dynamics ask “what if” questions

Constraints on Systems

  • No system can grow forever. There must be a reinforcing loop driving growth and a balancing loop constraining the growth
  • Nonrenewable resources are stock limited
  • Renewable resoruces are flow limited

Resilience, Self-Organization and Hierarchy

  • There are always limits to resilience
  • Systems need to be managed for resilience as well as productivity and stability
  • Hierarchichal systems evolve from the bottom up

Source of System Surprises

  • Many relationships in systems are non-linear
  • There are no separate systems. The world is a continuum. Where to draw a boundary around a system depends on the purpose of the discussion
  • At any given time, the input that is most importan to a system is the one that is most limiting
  • Any physical entitiy with multiple inputs and outputs is surrounded by layers of limits.
  • There will always be limits to growth
  • When there are long delays in feedback loops, some sort of foresight is essential
  • The bounded rationality of each actor in a system may not lead to decisions that further the welfare of the system as a whole

Mindset and Models

  • Everything we think we know about the world is a model
  • Our models do have a strong congruence with the world
  • Our models fall far short of representing the real world fully.

Springing the System Traps

Policy Resistance

Adding policy can sometimes have unintended consequences. Need to let go. The Tragedy of the Commons

The actors overause a shared resource when there is a weak feedback between the use and the consequences. Fix is to educate, also reinforce the feedback link. Drift to low performance

Allowing performance standards to be influenced by past performance, sets up a reinforcing feedback loop of eroding goals. Fix is to keep performance and standards absolute.

Escalation

When the state is determined by trying to surpass the state of another stock -and vice versa- then there is a reinforcing feedback loop carrying the system into an arms race. The way out is to avoid getting in it or refuse to compete.

Success to the Successful

The winners of a competition are systematically rewarded with the means to win again. The way out: Diversify

Shifting the Burden to the Intervenor

Shifting the burden, addiction arise when a solution to a systematic problem reduces or disguises the symptoms, but does nothing to solve the underlying problem. Way out: Don’t get in. Focus on the long term.

Rule Beating

Rules to govern a system can lead to rule-beating, perverse behavior that gives the appearance of obeying the rules or achieving the goals, but that actually distorts the systems. Way out: redesign the system.

Seeking the Wrong Goal

System may work to produce a result that is not intended and wanted. Specify indicators that reflect the real welfare of the system. Do not confuse effort with result.

Places to Intervene in a System Sorted by effectiveness

12 Numbers

11 Buffers

10 Stock-and-Flow Structures

9 Delays

8 Balancing Feedback Loops

7 Reinforcing Feedback Loops

6 Information Flows

5 Rules

4 Self-Organization

3 Goals

2 Paradigms

1 Transcending Paradigms

Guidelines for Living in a World of Systems

  1. Get the beat of the system

  2. Expose your mental models to the light of day

  3. Honor, respect and distribute information

  4. Use language with care and enrich it with system concepts

  5. Pay attention to what is important, not just what is quantifyiable

  6. Make feedback policies for feedback systems

  7. Go for the good of the whole

  8. Listen to the wisdom of the system

  9. Locate responsibility within the system

  10. Stay humble, stay a learner

  11. Celebrate complexity

  12. Expand time horizons

  13. Defy the disciplines

  14. Expand the boundary of caring

  15. Don’t erode the goal of goodness