134 PONTIFICIAE ACADEMIAE SCIENTIARVM SCRIPTA VARIA - 28 
The value of reproducible capital is several times that of 
national income. Errors arising from the conventional estimal- 
ing procedure may not be very considerable relative to cap- 
ital (1), but they will be significant in relation to the evaluation 
of depreciation and of G.N.P. 
The value of the grocer’s boy’s or of the waiter’s services 
should be counted as a production of capital; it is an element 
of gross investment and therefore of Gross National Product P. 
Demonstration of the Equality A =R, 
It is a simple matter, using the preceding formulation, to 
show the passage from A’ to A. Conventional accounting only 
considers as capital those goods whose longevity exceeds a 
certain duration. Thus with the notation of Table 2 (§ 111) 
the corresponding concept of the general model which is pre- 
sented in this paper is 
(116-14) A* = [ FR (2,6) db 
r J 
Le 
If the usual convention is modified and 6, made to tend to 
zero, then for A. =0 relation (111-1) gives 
(116-15) CC A=A*[9,=0]=R, . 
(') See below § 334, Table 8 and o. 
(*) In fact, under the usual concept the investment in a tool is con- 
sidered as made when this tool is put in service. With such a concept 
depreciation A’ includes interest. 
Nevertheless from an economic point of view, this is only an inter- 
mediate stage and the original investment takes place when the primary 
output (as defined in § 111) are supolied. 
[11] Allaic - pag. 38