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PONTIFICIAE ACADEMIAE SCIENTIARVM SCRIPTA VARIA - 28

principle. Often enough, an outlay which will to amortised
over 18 months will still be charged against operating expenses.
 Let 1; denote the practical limit.
Secondly, investments whose amortisation period is below
t; and which are accounted as operating expenses contain
both primary inputs and earlier inputs incorporated in the
existing supplies and equipment. Thus, minor maintenance
charges include at the same time wages, supplies produced
some time earlier and the reward for the use of equipment.
Thus the maintenance outlays which emerge into consumed
income before 1; include not only the primary inputs supplied
at moment ¢ but also primary inputs corresponding to goods
produced earlier. The primary inputs of moment £ enter consumed
 income before 1, and at least as a first approximation,
the second group of inputs can be considered as entering consumed

 income before (1, +6) where © is the average length
nf the production period with the year as time unit (%).
It may be assumed, at least as a first approximation that
the shares of the two categories of input are respectively proportional
 to

(334-23) A -

Ro

N=[f

 we consider the weighted average

(334-24)  O'=AT,+ (1-1) (1, +0)=1, + (1-1)

1) 0 is defined by relation (112-2).
2) Relation (333-5).

11] Allais - pag. 158