Flows can change very quickly if we want them to. It is easy to eat a big bowl of ice cream or go for a run around the neighborhood in a matter of minutes. However, stocks react much more slowly. Our weight doesn’t instantly drop or rise. It takes time. In a system, stocks usually change slowly. They can act as the buffers or delays for the system. They are the keepers of a system’s momentum. They reveal a great deal about why a system behaves the way it does.
