To proceed from assumptions about an abstract theoretical set-up and from them to draw conclusions about the observable world and to test - by rough … - Ragnar Frisch

In the last decade's intensive study of all sorts of social and economic time series, it has become clear, it seems to me, that the usual time series technique is not quite adequate for the purpose which the social investigator is pursuing... We want to find out on more or less empirical grounds what is actually present in the series at hand, that is to say, what sort of components the series contains.

… in economic political discussions there is a nearly infinite number of specific questions that may be asked. Besides the ones mentioned in section 3 consider for instance these: "Should we build a road between points A and B in the country?", "Should we promote investments that will give employment to many people, or should we on the contrary promote such investment which will save labour?"… "Should we put more emphasis on things that have up to now not been included in the statistical concept of the gross national product? For instance, should we try to avoid air-pollution and all the kinds of intoxications that may be caused by refuse and waste (a problem that must be studied in its totality as a problem of circulation of matter in society, much in the same way as we study interindustry relations in an input-output table)?“, “Should we assess economic value to an undisturbed nature?” etc.

The majority of the economic oscillations which we encounter seem to be explained most plausibly as free oscillations.