Flows change the stocks. To alter a stock, the flow must change rather dramatically. Stocks and flows are essential to understanding the dynamics of system change. This demonstrates the accelerator, a crucial system principle . Changes to stocks lead to accelerated changes in flows.
Assets change gradually while production swings widely.
When force levels are reduced, production jobs fall severely, and then rebound somewhat once a new steady state is reached. Executives testifying to Congress will want to communicate that job sensitivity when discussing defense changes. Then the steady state 100 aircraft fleet would require buying 5 aircraft per year instead of 10. Reducing the fleet to 80 in 5 years would mean buying 20 fewer aircraft, or no aircraft at all for 5 years, and upon reaching 80, increasing production to 4 per year. When aircraft last 20 years instead of 10, reducing the fleet by 20 percent in 5 years indicates a 100-percent reduction in production, followed by reopened production after 5 years of inactivity.