SEMAINE D'ÉTUDE SUR LE ROLE DE L’ANALYSE ECONOMETRIQUE ETC. 153 
are dealt with from the point of view of model building in non- 
experimental situations in general, not only in econometrics. 
The first point refers to the basic pluralism when it comes to 
model building for different purposes. Typical in this respect 
is the difference between short range and long range forecast- 
ing and the ensuing differences in the model construction. To 
bring the general perspective in relief, reference is made to 
similarities in this respect in economics and meteorology. 
Meteorology . . 24 or 
Economics 6 or 
Short range 
forecasts 
hou 
ve R 
months 
Long range 
forecasts 
4 or 6 weeks 
5 or 10 years 
In meteorology the short term forecasts are fairly reliable 
over 24 to 48 hours. The principal basis of the short term 
forecasting techniques is the thermodynamic theory of cyclons 
of the BERGEN school (?!). The importance of this theoretical 
innovation can be read off in the gradual increase in the reli- 
ability of the forecasts from 1920 or thereabout. 
Meteorological forecasts over the « long range » of 4 or 6 
weeks is a more recent development. Here the forecasting has 
to be based on other phenomena than the cyclons and their 
individual paths. The technique is still in its beginnings, and 
the reliability is much lower than for the short range forecasting. 
In economic forecasting, « short term » means ranges from 
3 or 6 months up to 6 or 8 quarters, and the model building 
here focusses on the boom-recession pulsations. « Long range » 
usually means something like 5 or 10 years, and the all- 
important purpose of the model is to analyze and forecast eco- 
nomic growth. Hence, just as in meteorology, the subject 
matter content of the economic model is radically different in 
short range and long range forecasting. On the other hand 
(*') J. BJERKNES (1919) is a basic reference. 
of the co-founders. see T. BERGERON (105g). 
For a recent review bv one 
.,» Wold - pag. 39