A rule that instructs the forecasting model (such as exponential smoothing) to adapt more quickly when it senses that a change in pattern has occurred. In many time-series forecasting methods, a trade-off can be made between smoothing randomness and reacting quickly to changes in the pattern. Judging from 12 empirical studies (Armstrong 1985, p. 171), this strategy has not been shown to contribute much to accuracy, perhaps because it does not use domain knowledge.