Modeling a complex system (causal loop)

Goal : Using systems thinking tools to model and understand the whole picture of a complex situation.

Onderwerpen - sujets
Charge de travail / werkdruk
Décisions Top-down beslissingen
Victimité et faible estime de soi - peu d'ambition - manque d'appropriation (gérer la boutique ensemble) - Slachtofferschap & laag gevoel van eigenwaarde - lage ambitie - gebrek aan eigenaarschap (samen de winkel runnen)

Explain concepts
Provide an example

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 football team is a system with elements such as players, coach, field, and ball. Its interconnections are the rules of the game, the coach’s strategy, the players’ communications, and the laws of physics that govern the motions of ball and players. The purpose of the team is to win games, or have fun, or get exercise, or make millions of dollars, or all of the above.

A school is a system. So is a city, and a factory, and a corporation, and a national economy. An animal is a system. A tree is a system, and a forest is a larger system that encompasses subsystems of trees and animals. The earth is a system. So is the solar system; so is a galaxy. Systems can be embedded in systems, which are embedded in yet other systems.

The elements of a system are often the easiest parts to notice, because many of them are visible, tangible things. The elements that make up a tree are roots, trunk, branches, and leaves. If you look more closely, you see specialized cells: vessels carrying fluids up and down, chloroplasts, and so on.

Once you start listing the elements of a system, there is almost no end to the process. You can divide elements into sub-elements and then sub-sub-elements. Pretty soon you lose sight of the system.

The interconnections in the tree system are the physical flows and chemical reactions that govern the tree’s metabolic processes—the signals that allow one part to respond to what is happening in another part. For example, as the leaves lose water on a sunny day, a drop in pressure in the water-carrying vessels allows the roots to take in more water. As the days get shorter in the temperate zones, a deciduous tree puts forth chemical messages that cause nutrients to migrate out of the leaves into the trunk and roots and that weaken the stems, allowing the leaves to fall.

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.

Some interconnections in systems are actual physical flows, such as the water in the tree’s trunk or the students progressing through a university. Many interconnections are flows of information—signals that go to decision points or action points within a system. These kinds of interconnections are often harder to see, but the system reveals them to those who look.

If information-based relationships are hard to see, functions or purposes are even harder. 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. Purposes are deduced from behavior, not from rhetoric or stated goals.

The power of a system :

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 is the memory of the history of changing flows within the system.
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Water in a reservoir behind a dam is a stock. The volume of wood in the living trees in a forest is a stock.

If you understand the dynamics of stocks and flows—their behavior over time—you understand a good deal about the behavior of complex systems. 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.

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.

Stocks usually change slowly. They can act as delays, lags, buffers, ballast, and sources of momentum in a system. Changes in stocks set the pace of the dynamics of systems. If you have a sense of the rates of change of stocks, you don’t expect things to happen faster than they can happen.

When a stock grows by leaps and bounds or declines swiftly or is held within a certain range no matter what else is going on around it, it is likely that there is a control mechanism at work. In other words, 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.

A feedback loop is formed when changes in a stock affect the flows into or out of that same stock. Think of an interest-bearing savings account in a bank. The total amount of money in the account (the stock) affects how much money comes into the account as interest. That is because the bank has a rule that the account earns a certain percent interest each year.

Feedback loops can cause stocks to maintain their level within a range or grow or decline.
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A feedback loop is a closed chain 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.

Balancing feedback loop If you’re a coffee drinker, when you feel your energy level run low, you may grab a cup of hot black stuff to perk you up again. You, as the coffee drinker, hold in your mind a desired stock level (energy for work). The purpose of this caffeine-delivery system is to keep your actual stock level near or at your desired level. (You may have other purposes for drinking coffee as well: enjoying the flavor or engaging in a social activity.) It is the gap, the discrepancy, between your actual and desired levels of energy for work that drives your decisions to adjust your daily caffeine intake.
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Balancing feedback loops are equilibrating or goal-seeking structures in systems and are both sources of stability and sources of resistance to change.

Reinforcing Feedback : “I’d need rest to refresh my brain, and to get rest it’s necessary to travel, and to travel one must have money, and in order to get money you have to work. . . . I am in a vicious circle . . . from which it is impossible to escape.” Honoré Balzac. 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.
When we were kids, the more my brother pushed me, the more I pushed him back, so the more he pushed me back, so the more I pushed him back.
The more soil is eroded from the land, the less plants are able to grow, so the fewer roots there are to hold the soil, so the more soil is eroded, so less plants can grow.
Reinforcing loops are found wherever a system element has the ability to reproduce itself or to grow as a constant fraction of itself.

Thinking in systems : When someone tells you that population growth causes poverty, you’ll ask yourself how poverty may cause population growth. You’ll be thinking not in terms of a static world, but a dynamic one. You’ll stop looking for who’s to blame; instead you’ll start asking, “What’s the system?”

An example
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.
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Picture a stock of car inventory in a store—a car dealership—with an inflow of deliveries from factories and an outflow of new car sales.
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Although this system still consists of just two balancing loops, what happens when the business experiences the same permanent 10-percent jump in sales from an increase in customer demand ?
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A single step up in sales causes inventory to drop. The car dealer watches long enough to be sure the higher sales rate is going to last. Then she begins to order more cars to both cover the new rate of sales and bring the inventory up. But it takes time for the orders to come in. During that time inventory drops further, so orders have to go up a little more, to bring inventory back up to ten days’ coverage. Eventually, the larger volume of orders starts arriving, and inventory recovers—and more than recovers, because during the time of uncertainty about the actual trend, the owner has ordered too much. She now sees her mistake, and cuts back, but there are still high past orders coming in, so she orders even less. In fact, almost inevitably, since she still can’t be sure of what is going to happen next, she orders too little. Inventory gets too low again. And so forth...

Why ? It’s because the car dealer is struggling to operate in a system in which she doesn’t have, and can’t have, timely information and in which physical delays prevent her actions from having an immediate effect on inventory.

A delay in a balancing feedback loop makes a system likely to oscillate.


Identify the individual events, their results, their causes in the system (nodes) - think about the roles involved in the process
Map them according to their relationships to one another (connections)
Qualify the nature of these relationships (+ / -)
Identify the possible loops and patterns and assess the overall impact of these
what’s driving the system?
what’s limiting the system? Rich countries transfer capital or technology to poor ones and wonder why the economies of the receiving countries still don’t develop, never thinking that capital or technology may not be the most limiting factors.
Are there any delays ? What are the effects of these?
Identify the actions needed to influence the positive results of the system
What would you change in the system ?

Wat heb je geleerd?
Wat neem je mee ?
Wat kan je ermee doen ?

Réfléchir aux applications possible du modèle:
quels sujets ?
quels cercles ?
comment l’appliquer ?

Denk na over de mogelijke toepassingen van het model:
welke situaties ?
welke cirkels?
hoe breng je het aan?
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