Stocks and Flows and Causal Loops

Simple stuff:

• "Stock and Flow" models keep track of conserved quantities aka stocks and their rates of change aka flows. How much water is in the bathtub, what's the bank account balance, or how many stars are in the galaxy are stocks. How fast does water come in from the tap or leave from the drain, what are all the deposits and withdrawals, or what's the rate of new star creation and old star destruction are flows.
  
  
• "Causal loop" diagrams depict the relationships, positive and negative, among actors and factors that make the decisions (or implement the functions) that make things happen. How much water do I want in the bathtub before I step in? What's the interest rate that money in my bank account earns? Where do the shock waves that can catalyze stellar formation come from, how long do stars live, and how big are the supermassive black holes that can eat them? What causes each of those factors to change, and what do they in turn cause to change?

"Stock and Flow" and "Causal Loop" graphs look somewhat similar and are easily confused. Key to good understanding and Systems Thinking is to distinguish them and use each in its proper place. Economist Michal Kalecki joked that "Economics is the science of confusing stocks with flows." Don't do that!

(cf Fifth Disciplinarians (2000-09-10), Systems Dynamics Advice (2017-07-12), Thinking in Systems (2017-11-03), The World We Truly Want(2018-10-13), Superpowers - Systems Thinking, Asking, and Listening (2019-01-29), Dancing with Systems (2019-06-21), Systems Thinking Icebergs (2019-06-27), Insight Modeling (2019-12-31), ...) - ^z - 2020-02-14