392

(IT.9)

PONTIFICIAE ACADEMIAE SCIENTIARVM SCRIPTA VARIA - 28

21,

x |
x,

don

a,

€

Ün—1,n
Ann

Kaa
Xi

a
k,_1 #-—1
Ay) Ang + <= Unn—1 Anky Cyn,

frees -
A 0

0)

0
© |

A few words may be added about the replacement coefficients.
 Each Ai (¢t=1, 2, ..., n—1I) represents the amount
of capital, in physical terms, which is required in each period
of time in order to keep productive capacity intact. This is the
general definition of the a; /'s. However, it may be useful to
adopt a simplification, because of its immediately apparent
meaning. We may assume that in each period of time and in
each sector, a constant proportion of the productive capacity
 vanishes owing to wear and tear, so that T;=1/a;
‘4=1, 2, ... n— I) represents a quantity which is very near
‘though, depending on the rate of growth of the sector, not
exactly coincidental with) the average life-time of physical
capital goods in sector :.
By now following exactly the same steps as in section 2,
the condition that must be satisfied in order that the system
may have non-trivial solutions emerges as

I
11.10) > Api iy + > Fan; Ain + > App; Crm = 4

[10] Pasinetti - pag. 22