Summary of Thinking in Systems by Donella Meadows: Part 2

Definition of a System

• A system isn’t just a random collection of things. It’s a connected set of elements that is organized in such a way that achieves something. In other words, a system consists of three things: elements, interconnections, and function or purpose.
• A professional football team is a system with elements such as players, coach, field, and ball. It’s interconnections are the rules of the game, the coach’s strategy, the players’ communication, and the laws of physics that govern the motions of the ball and players. The purpose of the team is to win games and make money.
• The elements of a system are often the easiest to notice, since many of them are tangible things. A university is a system that’s made up of buildings, students, professors, libraries, books, and computers.
• Elements can also be intangible. In the university, school pride and academic ranking are intangibles that could be important elements of the system.
• In many cases, it’s easier to learn about a system’s elements than about its interconnections. In the university, interconnections include the standards for admission, requirements for degrees, exams and grades, and the communication of knowledge.
• Some interconnections are physical flows, such as students moving throughout the university. Other interconnections are flows of information, which can be harder to see. For instance, students may use unofficial information about their chances of getting a good grade to decide which course to take. Governments need information about the kinds and qualities of pollution before they can create regulations to reduce that pollution.
• However, information about a problem may not be enough to trigger action. Information about resources, incentives, and consequences may also be necessary.

A System’s Purpose

• If information-based interconnections are hard to see, functions or purposes can be even harder.
• Purposes are determined from behavior, not from rhetoric or stated goals. If a government says it’s interested in protecting the environment but allocates little money or effort toward that goal, then environmental protection is not, in fact, the government’s purpose.
• Systems can be embedded within other systems. For instance, a tree is a system. An animal is a system. And a forest is a larger system that includes trees and animals.
• Since systems can be nested within systems, there can be purposes within purposes. The purpose of a university is to discover and preserve knowledge and pass it on to new generations. Within the university, the purpose of a student may be to get good grades, while the purpose of a professor may be to get tenure.
• Sub-purposes could come into conflict with the overall purpose. In the university, the student could cheat, and the professor could ignore the students in order to publish papers.
• Keeping sub-purposes and overall system purposes in harmony is an essential objective of successful systems.

Relative Importance in a System

• You can understand the relative importance of a system’s elements, interconnections, and purposes by imagining them changed one by one.
• Changing elements usually has the least effect on the system. If you change all the players on a football team, it’s still a football team. But since it may play much better or much worse as a result, particular elements in a system can indeed be important. The university has a constant flow of students and a slower flow of professors, but it’s still a university.
• A system usually goes on being itself, changing only slowly if at all. And this is the case, even with complete substitutions of its elements, as long as its interconnections and purposes remain intact.
• If the interconnections change, the system may be dramatically altered. It may even become unrecognizable, even though the elements remain the same.
• Change the rules from those of football to those of basketball, and you have a whole new ball game. If the students graded the professors, the place would no longer be a university.
• A change in function or purpose can also change a system profoundly, even if every element and interconnection remains the same. For instance, what if you keep the players and the rules, but change the purpose from winning to losing? What if the main purpose of a university was to win football games?

The Foundation of a System

• A stock is the foundation of any system. Stocks are the elements of the system that you can measure at any given time. It may be something you can see and count, such as water in a bathtub, a population, or money in a bank. And it doesn’t need to be physical, either. Your own self-confidence and supply of hope are both stocks as well.
• Stocks change over time through the actions of flow. Flows include inflows and outflows, filling and draining, deposits and withdrawals, and successes and failures.
• All system descriptions, however, are simplified versions of the real world.
• If you understand the dynamics of stocks and flows, or their behavior over time, you understand a good deal about the behavior of complex systems.
• Picture a bathtub that’s full of water, with its drain plugged up and its faucets turned off. This is an unchanging system. But if you pull the plug, the level of water goes down until the tub is empty.
• Again, imagine starting with a full tub, and again open the drain. But this time, when the tub is half full, turn on the inflow faucet so that the amount of water flowing in is equal to the amount flowing out. Now, the amount of water stays constant at the level it reached when the inflow became equal to the outflow.
• A stock is in dynamic equilibrium when its level doesn’t change despite inflows to and outflows from it. This is accomplished when all inflows are equal to all outflows.
• Now, imagine turning the inflow a little bit harder while keeping the outflow the same. The water level in the tub slowly rises.
• If you then turn the inflow faucet down again to match the outflow, the water in the tub will stop rising. Turn it down a little bit more, and the water level will fall slowly.

Important Systems Principles

• There are three important principles that apply to both simple and complex systems:
  1. As long as the sum of all inflows exceeds the sum of all outflows, the level of stock will rise.
  2. As long as the sum of all outflows exceeds the sum of all inflows, the level of stock will fall.
  3. If the sum of all inflows is equal to the sum of all outflows, the level of stock won’t change. It will stay in dynamic equilibrium at the level it happened to be when the two flows became equal.
• We tend to focus more on stocks than on flows. And even when we do focus on flows, we tend to focus more on inflows than on outflows. Therefore, you might miss seeing that you can fill a bathtub not only by increasing the inflow rate while keeping the outflow rate the same, but also by keeping the inflow rate the same while decreasing the outflow rate.
• You may be able to adjust inflows and outflows quickly, but it’s more difficult to change the level of stock quickly.
• You can adjust the faucet or drain of a bathtub quickly, but it’s more difficult to change the water level quickly. The tub can’t fill up immediately, even if the faucet is on full blast. And the water can’t be emptied instantly, even if you open the drain all the way.

Implications of Systems Principles

• Stocks, especially large ones, usually respond to change only by gradual filling or emptying. This is because flows take time to flow.
• The time lags that come from slowly changing stocks can cause problems in systems. But at the same time, this can also be a source of stability. For instance, a population that has learned many different skills doesn’t forget them immediately. In other words, the time lags imposed by stocks allow room to maneuver, to experiment, and to reverse policies that aren’t working.
• Most decisions are designed to regulate the levels in stocks. If inventory gets too high, prices may be cut or advertising costs may be increased, so that sales will go up and inventory will fall. If the amount of food in your fridge gets too low, you go to the grocery store and get more.
• People monitor stocks constantly and take action to either raise or lower their levels, or keep them within acceptable ranges.
• Systems thinkers see the world as a collection of stocks along with ways to regulate their levels by manipulating flows.

Balancing Feedback Loops

• A feedback loop is formed when changes in a stock affect the flows into or out of that same stock.
• One kind of feedback loop is called a balancing feedback loop. Balancing feedback loops try to keep a stock at a given value, or within a range of values. If you push a stock too far up, a balancing loop will try to push it back down, and vice versa.
• A cup of hot tea will gradually cool down to room temperature. And the loop works the other way too. Iced tea will warm up until it’s the same temperature as the room.
• Whatever the initial value of the system stock (tea temperature in this case), whether it’s above or below the goal (room temperature), the balancing feedback loop brings it toward the goal.
• The presence of a feedback mechanism doesn’t necessarily mean that it works well, though. For instance, the action that it triggers may not be strong enough. Or, information can arrive too late, at the wrong place, or be incomplete.

Reinforcing Feedback Loops

• The second kind of feedback loop is called a reinforcing feedback loop. It’s snowballing, creating a virtuous or vicious cycle that can cause healthy growth or runaway destruction. It generates more input to a stock the more that’s already there, and less input the less that’s already there.
• Think of a savings account that pays interest. The total amount of money in the account (the stock) affects how much money comes into the account (the inflow) as interest. The more money you have in the account, the more interest you earn. This interest is added to the money that’s already in the account, where it earns even more money in the form of interest.
• This kind of growth is not linear and constant, but exponential. It gets bigger and bigger, and happens faster and faster.
• The amount of time it takes for an exponentially growing stock to double in size is roughly equal to 72 divided by the growth rate, expressed as a percentage.
• If you put $100 in an investment that earns 3% interest per year, you’ll double your money in 24 years (72 / 3 = 24). But if you can earn 6% interest, your money will double in 12 years (72 / 6 = 12).
• Balancing and reinforcing feedback loops are basic to systems. Once you begin to see feedback loops all around you, you’re on your way to becoming a systems thinker.
• Instead of only seeing how A causes B, you’ll start to wonder how B may also influence A. Or how A might reinforce itself.
• Rather than looking for who’s to blame, you’ll start asking, “What’s the system?” The concept of feedback opens up the idea that a system can cause its own behavior.

To review part 1 of this summary, click here.

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