THINKING IN SYSTEMS
A system is a set of things (people, cells, molecules, etc) interconnected in such a way that they
produce their own pattern of behaviour over time. The system may be buffeted, constricted,
triggered or driven by outside forces. But, the system’s response to these forces is characteristic of
itself.
• For example: political leaders don’t cause recessions or economic booms. Ups and downs are
inherent in the structure of the market economy.
• Most of the real problems need to be fixed ‘inside’ instead of outside.
• Systems happen all at once; they are connected not just in one direction, but in many
directions simultaneously.
• The system-thinking lens allows us to reclaim our intuition about whole systems and:
o Hone our abilities to understand parts,
o See interconnections,
o Ask ‘what-if’ questions about possible future behaviours, and
o Be creative and courageous about system redesign.
CHAPTER 1
A system is an interconnected set of elements that is coherently organized in a way that achieves
something. A system must consist of three kinds of things: elements, interconnection and a function
or purpose.
• Systems can be embedded in systems, which are embedded in yet other systems. Think
about a three which is a system in a forest.
• A conglomeration without any particular interconnections or function is not a system.
• Systems can change, adapt, respond to events, seek goals, mend injuries and attend to their
own survival in lifelike ways, although they may contain or consist of non-living things.
• Systems can be self-organizing, and often are self-repairing over at least some range of
disruptions. They are resilient, and many of them are evolutionary. Out of one system other
completely new, never-before imagined systems can arise.
• Elements are most often the easiest part of the system to understand, because many of
them are visible, tangible things, but this isn’t necessary.
• Interconnections: the relationship that hold the elements together. Interconnections are
often harder to understand than the elements. Many interconnections are flow of
information – signals that go to decision points or action points within a system. Information
holds systems together and plays a great role in determining how they operate.
• A system’s function (nonhuman) or purpose (human) is not necessarily spoken, written, or
expressed explicitly, expect through the operation of the system. The best way to deduce the
system’s purpose is to watch for a while to see how the system behaves. Purposes are
deduced from behaviour, not from rhetoric or stated goals.
• To check the importance of system’s elements, interconnections, and purposes you can
change them one by one. The changing element that has the least effect on the system is the
least important. Think about changing all the football players in a team.
• Changing interconnections in a system can change it dramatically; so that you can’t recognize
it anymore. Change in function or purpose also can be drastic.
• All parts of the system are very important, but its function or purpose is often the most
crucial determinant of the system’s behaviour.
,A stock is the foundation of any system. Stocks are the elements of the system that you can see, feel,
count or measure at any given time.
• A system stock is just what it sounds like: a store, a quantity, an accumulation of material or
information that has built up over time.
• A stock does not have to be physical. For example: your supply of hope that the world can be
better is also a stock.
• Stocks change over time through the actions of a flow. A stock is the memory of the history
of changing flows within the system.
• You can draw the relationship between flows and stocks in a simplified version of the reality.
For example the amount of births and deaths and the size of the population.
• Dynamic equilibrium: a constant state, but with a continuous inflow and outflow. For
example when you have a bath tub, and open the drain and the tap at the same time.
• Principles of flow and stock:
o As long as the sum of all inflows exceed the sum of all outflows, the level of the stock
will rise.
o As long as the sum of all outflows exceed the sum of all inflows, the level of the stock
will fall.
o If the sum of all outflows equals the sum of all inflows, the stock level will not
change; it will be held in dynamic equilibrium at whatever level it happened to be
when the two sets of flows became equal.
• A stock can be increased by decreasing its outflow rate as well as by increasing its inflow rate
(with very different costs, most often decreasing its outflow is less expensive).
• A stock takes time to change, because flows take time to flow. Stocks usually change slowly.
Stocks, especially large ones, respond to change, even sudden change, only by gradual filling
or emptying. Stocks act as delays or buffers or shock absorbers in systems.
• Change in stocks set the pace of the dynamics of systems. The time lags that come from
slowly changing stocks can cause problems in systems, but they also can be sources of
stability.
• The presence of stocks allows inflows and outflows to be independent of each other and
temporarily out of balance with each other.
• People monitor stocks constantly and make decisions and take actions designed to raise or
lower stocks or to keep them within acceptable ranges. That means system thinkers see the
world as a collection of ‘feedback processes’.
, Feedback loop: is the consistent behaviour pattern over a long period of time that is the first hint of
the existence of a feedback loop. A feedback loop is formed when changes in a stock affect the flows
into or out of that same stock.
• A feedback loop is a closed cain of causal connections from a stock, through a set of decisions
or rules or physical laws or actions that are dependent on the level of the stock, and back
again through a flow to change the stock.
• Feedback loops can cause stocks to maintain their level within a range or grow or decline. In
any case, the flows into or out of the stock are adjusted because of changes in the size of the
stock itself. Whoever or whatever is monitoring the stock’s level begins a corrective process,
adjusting rates of inflow or outflow and so changing the stock’s level. The stock level feeds
back through a chain of signals and actions to control itself.
• Not all systems have feedback loops; the stocks don’t affect the flows.
• One common kind of feedback loop stabilizes the stock level. The stock level may not remain
completely fixed but is does stay within an acceptable range. There is a gap between the
actual and the desired level.
• The diagram is the examples are direction-free, because feedback loops often can operate in
two directions.
Balancing feedback loops are goal-seeking or stability-seeking and are both sources of stability and
sources of resistance to change. Each tries to keep a stock at a given value or within a range of values.
If you push a stock too far up, a balancing loop will try to pull it back down and the other way around.
The change is faster at first, and then slower, as the discrepancy between the stock and the goal
decreases.
Reinforcing feedback loops (amplifying, self-multiplying, snowballing): a vicious or virtuous circle that
can cause healthy grow or runaway destruction.
• Noted with a R.
• It generates more input to a stock the more that is already there (and less input the less that
is already there).
• Reinforcing loops are found wherever a system element has the ability to reproduce itself or
to grow as a constant fraction of itself. Think about populations and economies.
• The reinforcing feedback loop is the central engine of growth in an economy.
• Exponential growth (or decrease).
