SEMAINE D'ETUDE SUR LE ROLE DE L ANALYSE ECONOMETRIQUE ETC. 
_ 
West, or of the East, or of the Developing countries; these areas are 
defined in fact in terms of political tensions and interrelations which 
also are shifting over time. This band (points out something on 
blackboard) is the relation between East and West, and there is 
the Developing countries; so, the world system would consist of W, 
E and D and their interrelations. To some extent, Professor LEONTIEF 
has taken this into account in his paper in calculating what should 
go from either W or E to D. 
We thus have a kind of world system of W, E, and D. Then we 
have to consider also the national system of each particular country. 
In model making, there will continually be the need to think of the 
different national systems as constituent elements of the world 
system. However, there would be need of delimiting the sphere of 
‘nterest according to the purpose in view. We may have to consider 
a particular national system or a particular sector or groups of sectors 
within a national system. A nation or a country is, however, not 
the only basis of delimiting the sphere of interest. There will be 
many other ways of delimiting the system, for example, in external 
trade we have bilateral or multilateral systems. It seems to me that 
it would be a good step forward to have an agreed terminology in 
this whole business of model making. The two concepts « macro » 
and « micro » require to be arranged in some kind of a logical system 
of hierarchy involving dimensions in space, in terms of economic 
sectors, and also of time. It would be then possible to view the 
micro-models at different levels fitting into a macro-model at a 
higher level, and then these macro-models fitting into wider macro- 
models at still higher levels until the global world system is reached. 
Going back to my first point, if I have understood Professor 
STONE correctly, there would be need of taking into consideration 
experience or results of experiments to assess the validity of the 
model « M » in respect of the system of observations « O », and 
finally in relation to the world of reality « R ». When we speak of 
experience it would, I think, be of great help to keep in mind that 
a model developed in one country, on the basis of experience of that 
country, it may be verified or experimented upon, or modified in 
11 Stone - pag. So