SEMAINE D'ÉTUDE SUR LE ROLE DE L ANALYSE ECONOMETRIQUE ETC. 
v4.3 
assumed as an exogenous datum is the set of consumers’ pre- 
ferences. Thus, as time goes on, the shape of these consumers’ 
preferences and the movements of technical coefficients postul- 
ated by (V.2' determine the time movements of the ve 
may write 
V.3) 
cdg eee @ 
a 
dt [an .. 
a. 
a, IB: 
a 
Ah 
c 
where the fs depend on the shape of the consumers’ preferen- 
ces, which are defined in such a way as to satisfy propositions 
a), b), and c) of chapter IV section 6, graphically represented 
in fig. 1. The technical coefficients that appear in (V.3) in- 
duence the 7;’s through the medium of two channels: the level 
and the rate of change of real per-capita incomes, and the 
variation of the structure of prices. 
Here, for purposes of simplicity and symmetry, the assump- 
tion will be made that the movements of per-capita demand 
may approximately be broken down (if we represent them on 
a logarithmic diagram) into stretches of straight lines. In other 
words, we assume that time can be divided into finite stretches 
of length s (larger than the unit of time we are adopting) 
within which, for each commodity i, the percentage rate of 
change of demand 7, remains constant. Then passing from 
one stretch of time of length s to the next, r; changes, remain- 
ng then constant again for another stretch of time s And 
30 on. 
Therefore, bv defining now a new variable v as 
101 Pasinetti - pag. 73