The book Systems Thinking for Social Change reminded me of a common-sense principle that is often overlooked — the Bathtub Analogy. The concept is simple: the level of water in the tub is determined by the rate at which the water flows in and the rate at which it drains out. Too often, we only focus on the faucet.

The analogy is applied in many settings such as John Sterman’s Carbon Bathtub (describing the level of CO2 put into the atmosphere vs what nature can disburse) and the analogy framing homelessness (decrease the number becoming homeless/increase those moving to permanent housing). However, it can apply to many constructs in our organizational or personal life:

  • We can reduce the calories we eat to lose weight — or increase the number that we burn
  • We can increase hiring to expand staff — or reduce the attrition of current employees
  • We can reduce spending to meet our budget — or increase income
  • We can purge possessions to have more room — or increase storage space
  • We can increase new membership — or increase retention of those we serve

The Bathtub Analogy reminds us to pay attention to the flow rather than focusing only on the level. When we consider both inputs and outputs — and the relative rates at which they are occurring — often new solutions come to mind as well as a deeper and more nuanced understanding of the whole.

The next time you are trying to shift behavior, draw the system through the lens of a bathtub. The analogy might help you find solutions that otherwise would have gone down the drain.

Source: Systems Thinking for Social Change by David Peter Stroh, 2015

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