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If a factory is torn down but the rationality which produced it is left standing, then that rationality will simply produce another factory. If a revolution destroys a government, but the systematic patterns of thought that produced that government are left intact, then those patterns will repeat themselves.… There’s so much talk about the system. And so little understanding.
Managers are not confronted with problems that are independent of each other, but with dynamic situations that consist of complex systems of changing problems that interact with each other. I call such situations messes.… Managers do not solve problems, they manage messes.
Once we see the relationship between structure and behavior, we can begin to understand how systems work, what makes them produce poor results, and how to shift them into better behavior patterns.
A system is a set of things—people, cells, molecules, or whatever—interconnected in such a way that they produce their own pattern of behavior over time.
we have been taught to analyze, to use our rational ability, to trace direct paths from cause to effect, to look at things in small and understandable pieces, to solve problems by acting on or controlling the world around
It’s almost irresistible to blame something or someone else, to shift responsibility away from ourselves, and to look for the control knob, the product, the pill, the technical fix that will make a problem go away.
The behavior of a system cannot be known just by knowing the elements of which the system is made.
A system* is an interconnected set of elements that is coherently organized in a way that achieves something. If you look at that definition closely for a minute, you can see that a system must consist of three kinds of things: elements, interconnections, and a function or purpose.
A system is more than the sum of its parts. It may exhibit adaptive, dynamic, goal-seeking, self-preserving, and sometimes evolutionary behavior.
Many of the interconnections in systems operate through the flow of information. Information holds systems together and plays a great role in determining how they operate.
Purposes are deduced from behavior, not from rhetoric or stated goals.
An important function of almost every system is to ensure its own perpetuation.
Keeping sub-purposes and overall system purposes in harmony is an essential function of successful systems.
The least obvious part of the system, its function or purpose, is often the most crucial determinant of the system’s behavior.
games. A change in purpose changes a system profoundly, even if every element and interconnection remains the same.
Stocks are the elements of the system that you can see, feel, count, or measure at any given time.
Stocks change over time through the actions of a flow. Flows are filling and draining, births and deaths, purchases and sales, growth and decay, deposits and withdrawals, successes and failures.
dynamics of stocks and flows—their behavior over time—you understand a good deal about the behavior of complex systems.
state of dynamic equilibrium—its level does not change, although water is continuously flowing through it.
As long as the sum of all inflows exceeds the sum of all outflows, the level of the stock will rise. As long as the sum of all outflows exceeds the sum of all inflows, the level of the stock will fall. 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.
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. Everyone
A stock takes time to change, because flows take time to flow.
Stocks generally change slowly, even when the flows into or out of them change suddenly. Therefore, stocks act as delays or buffers or shock absorbers in systems.
The time lags imposed by stocks allow room to maneuver, to experiment, and to revise policies that aren’t working.
If you have a sense of the rates of change of stocks, you don’t expect things to happen faster than they can happen. You don’t give up too soon. You can use the opportunities presented by a system’s momentum to guide it toward a good outcome—much as a judo expert uses the momentum of an opponent to achieve his or her own goals.
The presence of stocks allows inflows and outflows to be independent of each other and temporarily out of balance with each other.
Stocks allow inflows and outflows to be decoupled and to be independent and temporarily out of balance with each other.
Human beings have invented hundreds of stock-maintaining mechanisms to make inflows and outflows independent and stable. Reservoirs enable residents and farmers downriver to live without constantly adjusting their lives and work to a river’s varying flow, especially its droughts and floods. Banks enable you temporarily to earn money at a rate different from how you spend. Inventories of products along a chain from distributors to wholesalers to retailers allow production to proceed smoothly although customer demand varies, and allow customer demand to be filled even though production rates
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People monitor stocks constantly and make decisions and take actions designed to raise or lower stocks or to keep them within acceptable ranges.
Systems thinkers see the world as a collection of stocks along with the mechanisms for regulating the levels in the stocks by manipulating flows. That means system thinkers see the world as a collection of “feedback processes.”
if you see a behavior that persists over time, there is likely a mechanism creating that consistent behavior. That mechanism operates through a feedback loop. It is the consistent behavior pattern over a long period of time that is the first hint of the existence of a feedback loop.
The second kind of feedback loop is amplifying, reinforcing, self-multiplying, snowballing—a vicious or virtuous circle that can cause healthy growth or runaway destruction. It is called a reinforcing feedback
Reinforcing loops are found wherever a system element has the ability to reproduce itself or to grow as a constant fraction of itself. Those elements include populations and economies.
Reinforcing feedback loops are self-enhancing, leading to exponential growth or to runaway collapses over time. They are found whenever a stock has the capacity to reinforce or reproduce itself.
The information delivered by a feedback loop—even nonphysical feedback—can only affect future behavior; it can’t deliver a signal fast enough to correct behavior that drove the current feedback. Even nonphysical information takes time to feedback into the system. Why is that important? Because it means there will always be delays in responding. It says that a flow can’t react instantly to a flow. It can react only to a change in a stock, and only after a slight delay to register the incoming information.
A stock-maintaining balancing feedback loop must have its goal set appropriately to compensate for draining or inflowing processes that affect that stock. Otherwise, the feedback process will fall short of or exceed the target for the stock.
Every balancing feedback loop has its breakdown point, where other loops pull the stock away from its goal more strongly than it can pull back.
systems often have several competing feedback loops operating simultaneously, those loops that dominate the system will determine the behavior.
Complex behaviors of systems often arise as the relative strengths of feedback loops shift, causing first one loop and then another to dominate behavior.
