Thinking in Systems: International Bestseller
Last read September 11, 2016
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Highlights
45 highlights.
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.
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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.
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An outside event may unleash that behavior, but the same outside event applied to a different system is likely to produce a different result.
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Because of feedback delays within complex systems, by the time a problem becomes apparent it may be unnecessarily difficult to solve.
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According to the competitive exclusion principle, if a reinforcing feedback loop rewards the winner of a competition with the means to win further competitions, the result will be the elimination of all but a few competitors.
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A diverse system with multiple pathways and redundancies is more stable and less vulnerable to external shock than a uniform system with little diversity.
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No one deliberately creates those problems, no one wants them to persist, but they persist nonetheless. That is because they are intrinsically systems problems—undesirable behaviors characteristic of the system structures that produce them.
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Systems thinkers call these common structures that produce characteristic behaviors “
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The behavior of a system cannot be known just by knowing the elements of which the system is made.
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A system* is an interconnected set of elements that is coherently organized in a way that achieves
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something.
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must consist of three kinds of things: elements, interconnections, and a function or purpose.
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Is there anything that is not a system?
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Yes—a conglomeration without any particular interconnections or function.
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You think that because you understand “one” that you must therefore understand “two” because one and one make two. But you forget that you must also understand “
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It’s easier to learn about a system’s elements than about its interconnections.
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If a government proclaims its interest in protecting the environment but allocates little money or effort toward that goal, environmental protection is not, in fact, the government’s purpose.
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Purposes are deduced from behavior, not from rhetoric or stated goals.
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An important function of almost every system is to ensure its own perpetuation.
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Keeping sub-purposes and overall system purposes in harmony is an essential function of successful systems.
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If the interconnections change, the system may be greatly altered. It may even become unrecognizable, even though the same players are on the team.
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Changing interconnections in a system can change it dramatically.
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A change in purpose changes a system profoundly, even if every element and interconnection remains the same.
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The elements, the parts of systems we are most likely to notice, are often (not always) least important in defining the unique characteristics of the system—unless changing an element also results
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in changing relationships or purpose
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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.
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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.
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A stock, then, is the present memory of the history of changing flows within the system.
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How to read stock-and-flow diagrams. In this book, stocks are shown as boxes, and flows as arrow-headed “pipes” leading into or out of the stocks. The small T on each flow signifies a “faucet;” it can be turned higher or lower, on or off. The “clouds” stand for wherever the flows come from and go to—the sources and sinks that are being ignored for the purposes of the present discussion.
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If you understand the dynamics of stocks and flows—their behavior over time—you understand a good deal about the behavior of complex systems.
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Systems thinkers use graphs of system behavior to understand trends over time, rather than focusing attention on individual events. We also use behavior-over-time graphs to learn whether the system is approaching a goal or a limit, and if so, how quickly.
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The amount of water in the tub stays constant at whatever level it had reached when the inflow became equal to the outflow. It is in a state of dynamic equilibrium—its level does not change, although water is continuously flowing through it.
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several important principles that extend to more complicated systems:
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• As long as the sum of all inflows exceeds the sum of all outflows, the level of the stock will rise.
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As long as the sum of all outflows exceeds the sum of all inflows, the level of the stock will fall.
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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.
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Everyone understands that you can prolong the life of an oil-based economy by discovering new oil deposits. It seems to be harder to understand that the same result can be achieved by burning less oil.
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A stock takes time to change, because flows take time to flow. That’s a vital point, a key to understanding why systems behave as they do. Stocks usually change slowly. They can act as delays, lags, buffers, ballast, and sources of momentum in a system. Stocks, especially large ones, respond to change, even sudden change, only by gradual filling or emptying.
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The time lags that come from slowly changing stocks can cause problems in systems, but they also can be sources of stability.
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The time lags imposed by stocks allow room to maneuver, to experiment, and to revise policies that aren’t working.
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The presence of stocks allows inflows and outflows to be independent of each other and temporarily out of balance with
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each other.
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Human beings have invented hundreds of stock-maintaining mechanisms to make inflows and outflows independent and stable.
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Systems thinkers see the world as a collection of stocks along with the mechanisms for regulating the levels in the stocks by manipulating flows.
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That means system thinkers see the world as a collection of “feedback processes.
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