Stocks and Flows

Biological Parallel

A bear's fat reserves (stock) accumulate from summer foraging (inflow) and deplete during hibernation (outflow). The bear doesn't track daily calories—it tracks the stock that determines winter survival. Every organism manages stocks (glycogen, ATP, water, nutrients) with flows that vary seasonally, cyclically, or chaotically. Understanding the stock's current level and rate of change is more critical than any single transaction.