Base120 · Systems

Stocks & Flows

SY · Systems

Distinguish accumulations from rates of change affecting them

Model code
SY3
Transformation
SY (Systems) — Identify leverage points, feedback structures, and emergent dynamics in whole systems.
Priority
3 of 20
Framework
HUMMBL Base120 — 120 mental models across 6 transformations

When to use

"Use when a system has accumulations (stocks) and rates of change (flows). Distinguish the two — stocks change only when flows change, and flows are constrained by stocks. Many system problems come from confusing the two."

Example

"A team's technical debt is a stock. The rate of new debt creation and the rate of debt repayment are flows. Reducing the debt (stock) requires either increasing repayment (outflow) or reducing new debt creation (inflow). Working harder on repayment without reducing creation is a losing battle."

Common misuse

"Trying to change a stock directly. Stocks change only through flows. If you want to reduce the stock of debt, you must change the flows (repayment rate, creation rate). Exhorting the team to reduce debt without changing flows is ineffective."

Also known as

Stock-Flow DynamicsAccumulation and Rate

Related models

SY6SY8DE12