Stocks can either be renewable or non-renewable.

A non-renewable stock is limited and eventually expires with use. A renewable stock is limited by flows, but continues to be available so long as the flows don’t effectively push it into a non-renewable position. Renewable resources have behaviors based on their usage and regeneration capabilities.rM3

  1. Donella H. Meadows and Diana Wright, Thinking in Systems: A Primer (White River Junction, Vt: Chelsea Green Pub, 2008). (See notes.)