Thinking in Systems: A Primer
Donella Meadows, 2008
Why does a problem keep coming back, no matter how many people get blamed and replaced? Donella Meadows shows that the way a family, a company or a country behaves depends a lot on how it is built. With simple pictures, from a bathtub to a thermostat, the book teaches you to notice what piles up and what drains away, what speeds itself up or calms itself down, and where the response comes too late. It also teaches you to find the places where a small push changes a lot.
Who it is for
For anyone tired of solving the same problem over and over: at work, with money, at home. And for anyone who manages people, projects or their own life and wants to understand why good decisions so often lead to bad results.
But be careful! There is a danger that you will become a systems thinker!
A spring that bounces on its own
Donella Meadows began her classes with a children’s toy. A Slinky is a long, soft spring that can “walk” down stairs. Meadows would rest the spring on her palm, hold the top coil with the fingers of her other hand, and then take the lower hand away. The spring would start bouncing up and down. “Why does it behave like that?” Meadows would ask. The students would answer: “Because you took your hand away.”
Then she would rest the toy’s box on her palm and take her hand away in the same way. The box simply hung there. So the hand was not the reason. The spring bounces on its own, because that is how it is built. The hand only lets it happen.
Meadows was a scientist and one of the authors of the famous book The Limits to Growth. In Thinking in Systems she shows that many of our troubles work the same way as the spring. We are used to looking for someone to blame on the outside: a competitor, a boss, the government. But in the author’s view, the cause of a problem that never goes away often sits in how the situation itself is built. A system, as she defines it, is a set of parts that are connected to each other and work together toward some purpose: a family, a team, a company, a city, your own body.
Ahead are five simple pictures: a bathtub, a thermostat, a car dealership with late orders, a shared pasture and an electricity meter in the front hall. They will make it clear why good intentions so often lead to bad results, and where to push to make something really change.
You can fill a bathtub just by partly closing the drain
Picture a bathtub. The tap is open, and so is the drain. Meadows believes that anyone who has ever filled a bathtub already understands the main thing about systems. The water in the tub is a stock: something that builds up and can be measured at any moment. The water from the tap is a flow coming in, an inflow, and the water going down the drain is a flow going out, an outflow.
The rules are simple. If more pours from the tap than goes down the drain, the level rises. If less, the level falls. If the two are equal, the level stays put, even though water keeps flowing all the time. The author has a name for this state: dynamic equilibrium.
A stock can be anything: money in an account, books in a store, a forest, even self-confidence. And every stock has its own tap and its own drain.
The author notices two habits of ours. We look at the stock itself and forget about the flows. And of the two flows, we mostly notice the tap. It seems that only a new oil field can help the oil industry. But saving oil gives the same result. It’s just that different people benefit from it. Closing the drain can be as useful as opening the tap. A company can keep the same number of employees by hiring new people, or by keeping the ones who already work there. These are two different strategies with two different costs.
The second key idea: a stock changes slowly. A bathtub won’t fill in a second, even if you open the tap all the way. A forest won’t grow overnight, and new factories won’t be built in a month. So for a while the system keeps behaving the old way, even when we have already changed everything. Meadows advises not giving up too early: if you understand how fast a stock changes, you won’t expect change to come faster than it can.
Slowness has a good side too. A stock works like a safety cushion. Money in an account lets you spend more than comes in for a while, and a warehouse lets a store keep selling even if a delivery is late.
Try looking at whatever worries you in this way. If you’re short of money, energy or time, find the drain first, that is, figure out where it all goes. Plugging a leak is often easier and cheaper than opening the tap wider.
About the author
Donella Meadows (1941–2001) was an American scientist, a chemist and biophysicist with a doctorate from Harvard University. She was one of the main authors of The Limits to Growth (1972). She finished the draft of this book in 1993, and it was published after her death, in 2008.
All books by this author: Donella Meadows
Terms from the book
- Feedback
- Stock
- Flow
- Balancing loop
- Reinforcing loop
- Simon
- Forrester
- Paradigm
- Slinky: A children’s toy: a long, soft spring that bounces and can “walk” down stairs. Meadows brought one to her first classes.
- System: Parts that are connected to each other and together work toward some purpose: a team, a company, a forest, the human body. As the author defines it, a system has elements, connections and a purpose.
- Dynamic equilibrium: A state in which the level of a stock stays the same even though something keeps flowing through it: the inflow equals the outflow.
- Delay: The time that passes before an event is noticed and before the response to it takes effect. According to the author, delays are the most common cause of swings in a system.
- Hardin: Garrett Hardin (1915–2003), an American ecologist. In a 1968 article he described the trap of the shared pasture, which he called the tragedy of the commons.
- Tragedy of the commons: A trap in which a shared resource is used up by people who each do what is best for themselves: one person gets the gain, and the harm is split among everyone.
- Bounded rationality: Decisions that make sense from where a person stands, but turn out badly for the system as a whole, because that person can’t see the full picture.
- Drift to low performance: A trap from the book: poor results slowly lower the bar, a lower bar means people try less, and the results fall even further.
- Leverage points: Places in a system where a small change can greatly change how it behaves. The author put them in a list of twelve and asked readers not to treat it as a recipe.
- Gross national product: The total value of the goods and services a country produced in a year. Meadows sees it as a poor measure of success: it grows from both useful and harmful things.
All terms
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