SEMAINE D'ÉTUDE SUR LE ROLE DE L’ANALYSE ECONOMETRIQUE ETC. 20 
4 
À 
DUAL MODEL OF ECONOMIC GROWT.x 
[. A NEW DEVELOPMENT 
[ shall now exemplify the ideas on model-building expres- 
sed in the first section of the preceding chapter in terms of the 
model of the British economy on which I and my colleagues 
are working. Four progress reports on this work have already 
appeared in this series [7] [8] [9] [10]. In the first of these 
we began by setting up a single model for a future state of 
steady growth and, in our conclusions, hinted at the need for 
an extension of the model which would help us to plot out a 
path from the present to the future state. This extension is 
now beginning to take shape. 
In this short chapter, I shall outline the two parts of the 
model and explain how they interact. In chapter IV, I shall 
review in greater detail the structure of the first part, our origi- 
nal model, and discuss a number of modifications we are bring- 
ing to it. Finally, in chapter V, I shall describe the structure of 
‘he second part, on which we have recently started work. 
[n my exposition I shall try to bring out: the organic cha- 
cacter of the model, that is, how its structure and relationships 
tend to change as knowledge is accumulated; the receptiveness 
of the model to observations from different sources, including 
sstimates from industrial experts and others, which can im- 
prove its realism; and the degree of consistency which we trv to 
impose on the model F--" 
1] Stone - pag. 2,