ABSTRACT
In almost all the time series we meet with in econometrics and also in other series we find certain typical patterns, such as short cycles, long-run cycles, secular growth, etc. These types of fluctuations may have different theoretical explanations. Some cycles may be explained as forced oscillations, for example seasonal variations. Others may find their explanation in the form of dynamic relationships. In fact, I have given you examples showing how the structural form of dynamic relations can determine the form of the time curves, and I have shown you how the oscillations of such a dynamic system can be maintained by random shocks. This is the theoretical and explanatory point of view.
