Thinking In Systems Quotes

“Renewable resources are flow-limited. They can support extraction or harvest indefinitely, but only at a finite flow rate equal to their regeneration rate. If they are extracted faster than they regenerate, they may eventually be driven below a critical threshold and become, for all practical purposes, nonrenewable.”
― Donella H. Meadows, Thinking in Systems: A Primer

“Nonrenewable resources are stock-limited. The entire stock is available at once, and can be extracted at any rate (limited mainly by extraction capital). But since the stock is not renewed, the faster the extraction rate, the shorter the lifetime of the resource.”
― Donella H. Meadows, Thinking in Systems: A Primer

“The limits on a growing system may be temporary or permanent. The system may find ways to get around them for a short while or a long while, but eventually there must come some kind of accommodation, the system adjusting to the constraint, or the constraint to the system, or both to each other.”
― Donella H. Meadows, Thinking in Systems: A Primer

“Whenever we see a growing entity, whether it be a population, a corporation, a bank account, a rumor, an epidemic, or sales of a new product, we look for the reinforcing loops that are driving it and for the balancing loops that ultimately will constrain it. We know those balancing loops are there, even if they are not yet dominating the system’s behavior, because no real physical system can grow forever.”
― Donella H. Meadows, Thinking in Systems: A Primer

“Growth in a constrained environment is very common, so common that systems thinkers call it the “limits-to-growth” archetype.”
― Donella H. Meadows, Thinking in Systems: A Primer

“any physical, growing system is going to run into some kind of constraint, sooner or later. That constraint will take the form of a balancing loop that in some way shifts the dominance of the reinforcing loop driving the growth behavior, either by strengthening the outflow or by weakening the inflow.”
― Donella H. Meadows, Thinking in Systems: A Primer

“Delays are pervasive in systems, and they are strong determinants of behavior. Changing the length of a delay may (or may not, depending on the type of delay and the relative lengths of other delays) make a large change in the behavior of a system.”
― Donella H. Meadows, Thinking in Systems: A Primer

“A delay in a balancing feedback loop makes a system likely to oscillate.”
― Donella H. Meadows, Thinking in Systems: A Primer

“Complex behaviors of systems often arise as the relative strengths of feedback loops shift, causing first one loop and then another to dominate behavior.”
― Donella H. Meadows, Thinking in Systems: A Primer

“This behavior is an example of shifting dominance of feedback loops. Dominance is an important concept in systems thinking. When one loop dominates another, it has a stronger impact on behavior. Because systems often have several competing feedback loops operating simultaneously, those loops that dominate the system will determine the behavior.”
― Donella H. Meadows, Thinking in Systems: A Primer

“A population has a reinforcing loop causing it to grow through its birth rate, and a balancing loop causing it to die off through its death rate.”
― Donella H. Meadows, Thinking in Systems: A Primer

“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.”
― Donella H. Meadows, Thinking in Systems: A Primer

“There’s an important general principle here, and also one specific to the thermostat structure. First the general one: The information delivered by a feedback loop can only affect future behavior; it can’t deliver the information, and so can’t have an impact fast enough to correct behavior that drove the current feedback. A person in the system who makes a decision based on the feedback can’t change the behavior of the system that drove the current feedback; the decisions he or she makes will affect only future behavior.”
― Donella H. Meadows, Thinking in Systems: A Primer

“The thermostat is set at 18°C (65°F) in this simulation, but the room temperature levels off slightly below 18°C (65°F). That’s because of the leak to the outside, which is draining away some heat even as the furnace is getting the signal to put it back. This is a characteristic and sometimes surprising behavior of a system with competing balancing loops. It’s like trying to keep a bucket full when there’s a hole in the bottom. To make things worse, water leaking out of the hole is governed by a feedback loop; the more water in the bucket, the more the water pressure at the hole increases, so the flow out increases!”
― Donella H. Meadows, Thinking in Systems: A Primer

“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.”
― Donella H. Meadows, Thinking in Systems: A Primer

“Reinforcing loops are found wherever a system element has the ability to reproduce itself or to grow as a constant fraction of itself.”
― Donella H. Meadows, Thinking in Systems: A Primer

“It generates more input to a stock the more that is already there (and less input the less that is already there). A reinforcing feedback loop enhances whatever direction of change is imposed on it.”
― Donella H. Meadows, Thinking in Systems: A Primer

“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”
― Donella H. Meadows, Thinking in Systems: A Primer

“Feedbacks—the interconnections, the information part of the system—can fail for many reasons. Information can arrive too late or at the wrong place. It can be unclear or incomplete or hard to interpret. The action it triggers may be too weak or delayed or resource-constrained or simply ineffective.”
― Donella H. Meadows, Thinking in Systems: A Primer

“Balancing feedback loops are equilibrating or goal-seeking structures in systems and are both sources of stability and sources of resistance to change.”
― Donella H. Meadows, Thinking in Systems: A Primer

“Balancing feedback loops are goal-seeking or stability-seeking. Each tries to keep a stock at a given value or within a range of values. A balancing feedback loop opposes whatever direction of change is imposed on the system. If you push a stock too far up, a balancing loop will try to pull it back down. If you shove it too far down, a balancing loop will try to bring it back up.”
― Donella H. Meadows, Thinking in Systems: A Primer

“This kind of stabilizing, goal-seeking, regulating loop is called a balancing feedback loop,”
― Donella H. Meadows, Thinking in Systems: A Primer

“A feedback loop is formed when changes in a stock affect the flows into or out of that same stock. A feedback loop can be quite simple and direct.”
― Donella H. Meadows, Thinking in Systems: A Primer

“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.”
― Donella H. Meadows, Thinking in Systems: A Primer

“People monitor stocks constantly and make decisions and take actions designed to raise or lower stocks or to keep them within acceptable ranges. Those decisions add up to the ebbs and flows, successes and problems, of all sorts of systems.”
― Donella H. Meadows, Thinking in Systems: A Primer

“Most individual and institutional decisions are designed to regulate the levels in stocks. If inventories rise too high, then prices are cut or advertising budgets are increased, so that sales will go up and inventories will fall. If the stock of food in your kitchen gets low, you go to the store.”
― Donella H. Meadows, Thinking in Systems: A Primer

“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,”
― Donella H. Meadows, Thinking in Systems: A Primer

“There is one more important principle about the role of stocks in systems, a principle that will lead us directly to the concept of feedback. The presence of stocks allows inflows and outflows to be independent of each other and temporarily out of balance with each other.”
― Donella H. Meadows, Thinking in Systems: A Primer

“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.”
― Donella H. Meadows, Thinking in Systems: A Primer

“People often underestimate the inherent momentum of a stock. It takes a long time for populations to grow or stop growing, for wood to accumulate in a forest, for a reservoir to fill up, for a mine to be depleted.”
― Donella H. Meadows, Thinking in Systems: A Primer