AI reviewed · sources pending. Book associations have not been verified.
Stocks and flows
ConceptStocks accumulate; inflows and outflows change their amounts over time.
Explanation or usage
A stock is an amount measured at a moment, such as water in a tank. A flow is a rate of change, such as liters entering per minute. The stock increases when total inflow exceeds total outflow, so reducing inflow alone does not necessarily make the stock fall.
Common misunderstandings
A smaller inflow necessarily means a shrinking stock.
In Thinking in systems
General context reviewed · book attribution and sources pending
Distinguish a quantity from a rate; numerical examples are illustrative.