A more or less general regularity in a process.
Different trends appear according to time horizon. Some are related to short, other to median, long or very long term (in a relative sense). These different time scales are interconnected and the observer must define the process level in which he/she is specifically interested, in view that any trend is normally related to a specific aspect of the process. The simple statistic analysis of data proposed by operation research and called trend analysis, while technically useful, is insufficient and even risky as a forecasting tool, if short term trends are not distinguished as fluctuations in the longer term trends (at various time horizons at that!).
In systems in dynamic equilibrium, the longer term trend generally constitutes a limiting frame for the oscillations of the shorter ones. When the short term trend line nears the limit (superior or inferior) of the longer one, a reversal of the short one generally takes place and a short term threshold is crossed. For this reason, any extrapolation of a shorter term trend is risky and doubtful, if nothing is known about the longer ones.
Of course, the time scales of trends observations are conventional as they depend on the type of processes which are observed.
While one day is a long span in a mayfly's life, one year amounts to practically nothing at geological scale. However, even in this case, a sudden discontinuity may happen at any time, as a chaotic event: an earthquake produced by the slow evolution of a geological fault.
Short term trends may appear as being random if related to long term ones. However, they may well depend from some micro-determinism whose visible expression may even be statistical. In this sense, M. BELlS states: "During the progress of some phenomenon, the necessity, as dominant trend, opens its way through the multiplicity of fortuitous events" (1987, p.59).
While no prediction can ever be absolutely guaranteed, the observation of long term trends combined with shorter ones is the most reliable tool at our disposal.
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To cite this page, please use the following information:
Bertalanffy Center for the Study of Systems Science (2020). Title of the entry. In Charles François (Ed.), International Encyclopedia of Systems and Cybernetics (2). Retrieved from www.systemspedia.org/[full/url]
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