The universe is not static. And demands and supplies are particularly dynamic. Intuitively I see no reason why penetration percentage can't wax and wane with

The universe is not static. And demands and supplies are particularly dynamic. Intuitively I see no reason why penetration percentage can't wax and wane with time due to changes in supplies, demands, populations, behaviors etc. He obviously understands the implications of shifts in demand given his "what you count" argument. Why bother stating a "law" if you can see its own holes?