Basics

A system must consist of three kinds of things: elements, interconnections, and a function or purpose.⊕ (Meadows 2008, chap. 1)

How to know whetehr your are looking at a system or just a bunch of stuff:

1. Can you identify parts? … and
2. Do the parts affect each other? … and
3. Do the parts together produce an effect that is different from the effect of each part on its own? … and perhaps
4. Does the effect, the behavior over time, persist in a variety of circumstances?⊕ (Meadows 2008, chap. 1)
   
   

It is easier to learn about a system’s elements than about its interconnections.⊕ (Meadows 2008, chap. 1)

Many interconnections are flows of information⊕ (Meadows 2008, chap. 1)

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An important function of almost every system is to ensure its own perpetuation.⊕ (Meadows 2008, chap. 1)

Any of those sub-purposes could come into conflict with the overall purpose … Keeping sub-purposes and overall system purpose in harmony is an essential function of successful systems.⊕ (Meadows 2008, chap. 1)

The human mind seems to focus more easily on stocks than on flows. On top of that, when we do focus on flows, we tend to focus on inflows more easily than on outflows. Therefore, we sometimes miss seeing that we can fill a bathtub not only by increasing the inflow rate, but also by decreasing the outflow rate.⊕ (Meadows 2008, chap. 1)

A feedback loop is formed when changes in a stock affect the flows into or out of that same stock.⊕ (Meadows 2008, chap. 1)

There are 2 types of feedback loops: * “Balancing feedback loops are goal seeking or stability seeking” * “A reinforcing feedback loop enhances whatever direction of change is imposed on it”⊕ (Meadows 2008, chap. 1)

The time it takes for an exponentially growing stock to double in size, the “doubling time,” equals approximately 70 divided by the growth rate (expressed as a percentage).⊕ (Meadows 2008, chap. 1)