Fast and slow variables are variables associated with processes that take place fast or slow depending on their scale. In complex systems there are many processes of change taking place in parallel on different levels, the macro-level processes of change typically take place very slowly; within ecology, these are called slow variables. Micro-level processes of change happen much faster and they have fast variables associated with them. Fast variables are factors that change rapidly and that are most easily measured and immediately altered by some system of management. These fast variables can be controlled by centralized regulatory systems such as a central bank reducing interest rates or putting liquidity into the market in order to effect the state of the system immediately. However, slow variables can not be affected by centralized regulatory systems as they are an emergent outcome of long-term processes of evolution which take place in a distributed fashion.