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The Growth and Underinvestment Archetype is one of the common system archetype patterns defined as part of the system dynamics discipline. System dynamics is an approach which strives to understand, describe and optimize nonlinear behaviors of complex systems over time, using tools such as feedback loops in order to find a (leverage point ) of the system. As part of this discipline, several commonly found patterns of system behavior were found, named and described in detail. The Growth and Underinvestment Archetype is one of such patterns. == Elements of Archetype == The system described in the Growth and Underinvestment Archetype consists of three feedback loops. Each feedback loop can be one of two types: * Reinforcing loop – A reinforcing loop is a type of a feedback loop, where a positive increase of variable A causes an increase in variable B, which then in turn causes a positive increase in variable A. The behavior of such system in time is an exponential increase in both variables A and B. As an example, consider the behavior of a long-term bank savings account. As your savings accumulate, the more interest per time period you receive, further increasing the balance on your savings account. This is the crowning principle of retirement planning schemes, such as the American 401k pension system. In many cases however, there is a balancing loop to prevent the reinforcing behavior from occurring indefinitely. * Balancing loop – A balancing loop is a type of a feedback loop, where a positive increase of variable A causes a decrease in variable B, which in turn causes a positive increase in variable A. The behavior of such a system leads to the system finding stable a stable state over time. Consider the behavior of a thermometer. The thermometer is a very simple device in its core. If the measured temperature exceeds a certain preconfigured value, the heating is turned off. Otherwise the heating is turned on. The heating in turn influences the temperature, forcing the thermometer to reevaluate its behavior periodically. Since there is a delay in the system (it takes a while for the room to heat up after the heating has been turned on), the temperature in the room will oscillate around the preconfigured value. This happens because when the heating is turned on, it doesn’t have an immediate effect (the body emitting heat must warm up first), causing the temperature to fall below desired level. The same effect is in play when the temperature exceeds the desired value and the heating is turned off, since it takes a while for the heating body to cool down, causing further undesired temperature increases. This behavior could be potentially mitigated by setting two separate temperature thresholds, a lower one as a signal for the heating to activate and a higher one as a signal for the heating to deactivate. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Growth and underinvestment」の詳細全文を読む スポンサード リンク
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