[발췌: 일반이론 6장 부록] Appendix on User Cost

출처: The General Theory of Employment, Interest and Money (Keynes, 1936)
자료: MIA(html); eBook; single PDF; Gutenberg.au (cf. my catalog of his writings)

※ This is a reading note with excerpts taken, and personal annotations and remarks added, in trying to understand the above text, so visit the source links to see the original.

※ 발췌(excerpts):

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Appendix (to chapter 6) on User Cost 

I

User cost has, I think, an importance for the classical theory of value which has been overlooked. There is more to be said about it than would be relevant or appropriate in this place. But, as a digression, we will examine it somewhat further in this appendix.

  An entrepreneur's user cost is by definition equal to 

A1＋(G'－B')－G , [※＝ (G'－B')－(G－A1) 6장 처음]

where A1 is the amount of our entrepreneur's purchases from other entrepreneurs, G the actual value of his capital equipment at the end of the period, and G' the value it might have had at the end of period if he had refrained from using it and had spent the optimum sum B' on its maintenance and improvement. Now [:] 

• G－(G'－B'), namely the increment in the value of the entrepreneur's equipment beyond the net value which he has inherited from the previous period, represents the entrepreneur's current investment in his equipment and can be written I. 
• Thus U, the user cost of his sales-turnover A, is equal to A1－I [U＝ A1＋(G'－B')－G＝A1－{G－(G'－B')}＝A1-I] where A1 is what he has bought from other entrepreneurs and I  is what he has currently invested in his own equipment. 

A little reflection will show that all this is no more than common sense.

• Some part of his outgoings to other entrepreneurs is balanced by the value of his current investment in his own equipment, and the rest represents the sacrifice which the output he has sold must have cost him over and above the total sum which he has paid out to the factors of production. 
• ※ 다른 생사단위로부터 구매한 비용(A1) 중 일부는 당기 투자로 실현되어 생산장비에 반영(I), 따라서 A1－I 는 다른 요소비용을 제외한 사용자비용(user cost)이다.

If the reader tries to express the substance of this otherwise, he will find that its advantage lies in its avoidance of insoluble (and unnecessary) accounting problems. There is, I think, no other way of analysing the current proceeds of production unambiguously. If industry is completely integrated or if the entrepreneur has bought nothing from outside, so that A1＝0, the user cost is simply the equivalent of the current disinvestment involved in using the equipment; but we are still left with the advantage that we do not require at any stage of the analysis to allocate the factor cost between the goods which are sold and the equipment which is retained. Thus we can regard the employment given by a firm, whether integrated or individual, as depending on a single consolidated decisionㅡa procedure which corresponds to the actual interlocking character of the production of what is currently sold with total production. 

  The concept of user cost enables us, moreover, to give a clearer definition than that usually adopted of the short-period supply price of a unit of a firm's saleable output. For short-period supply price is the sum of the marginal factor cost and the marginal user cost. 

  Now in the modern theory of value it has been a usual practice to equate the short-period supply price to the marginal factor cost alone. It is obvious, however, that this is only legitimate if marginal user cost is zero or if supply price is specially defined so as to be net of marginal user cost, just as I have defined (p.24 above) ‘proceeds’ and ‘aggregate supply price’ as being net of aggregate user cost. But, whereas it may be occasionally convenient in dealing with output as a whole to deduct user cost, this procedure deprives our analysis of all reality if it is habitually (and tacitly) applied to the output of a single industry of firm, since it divorces the ‘supply price’ of an article from any ordinary sense of its ‘price’; and some confusion may have resulted from the practice of doing so. It seems to have been assumed that 'supply price' has an obvious meaning as applied to a unit of the saleable output of an individual firm, and the matter has not been deemed to require discussion. Yet the treatment both of what is purchased from other firms and of the wastage of the firm's own equipment as a consequence of producing the marginal output involves the whole pack of perplexities which attend the definition of income. For, even if we assume that the marginal cost of purchases from other firms involved in selling an additional unit of output has to be deducted from the sale-proceeds per unit in order to give us what we mean by our firm's supply price, we still have to allow for the marginal disinvestment in the firm's own equipment involved in producing the marginal output. Even if all production is carried on by a completely integrated firm, it is still illegitimate to suppose that the marginal user cost is zero, i.e. that the marginal disinvestment in equipment due to the production of the marginal output can generally be neglected. 

The concepts of user cost and of supplementary cost also enable us to establish a clearer relationship between long-period supply price and short-period supply price. Long-period cost must obviously include an amount to cover the basic supplementary cost as well as the expected prime cost appropriately averaged over the life of the equipment. That is to say, the long-period cost of the output is equal to the expected sum of the prime cost and the supplementary cost; and, furthermore, in order to yield a normal profit, the long-period supply price must exceed the long-period cost thus calculated by an amount determined by the current rate of interest on loans of comparable term and risk, reckoned as a percentage of the cost of the equipment. Or if we prefer to take a standard 'pure' rate of interest, we must include in the long-period cost a third term which we might call the risk-cost to cover the unknown possibilities of the actual yield differing from the expected yield. Thus the long-period supply price is equal to the sum of the prime cost, the supplementary cost, the risk cost and the interest cost, into which several components it can be analysed. The short-period supply cost, on the other hand, is equal to the ^marginal^ prime cost. The entrepreneur must, therefore, expect, when he buys or construct his equipment, to cover his supplementary cost, his risk cost and his interest cost out of the excess of the marginal value of the prime cost over its average value; so that in long-period equilibrium the excess of the marginal prime cost over the average prime cost is equal to the sum of the supplementary, risk and interest costs.[1]

  The level of output, at which marginal prime cost is exactly equal to the sum of the average prime ans supplementary costs, has a special importance, because it is the point at which the entrepreneur's trading account breaks even. It corresponds, that is to say, to the point of zero net profit; whilst with a smaller output than this he is trading at a net loss.

  The extent to which the supplementary cost has to be provided for apart from the prime cost varies very much from one type of equipment to another. Two extreme cases are the following:

(i) ...
(ii) ...

It may be worth pointing out that an entrepreneur does not use his oldest and worst equipment first, merely because its user cost is low; since its low user cost may be outweighed by its relative inefficiency, i.e. by its high factor cost. Thus an entrepreneur uses by preference that part of his equipment for which the user cost plus factor cost is least per unit of output.[2] It follows that for any given volume of output of the product in question there is a corresponding user cost,[3] but that this total user cost does not bear a uniform relation to the marginal user cost, i.e. to the increment of user cost due to an increment in the rate of output.


II

User cost constitutes one of the links between the present and the future. for in deciding his scale of production an entrepreneur has to exercise a choice between using up his equipment now and preserving it to be used later on. It is the expected sacrifice of future benefit involved in present use which determines the amount of the user cost, and it is the marginal amount of this sacrifice which, together with the marginal factor cost and the expectation of the marginal proceeds, determines his scale of production. How, then, is the user cost of an act of production calculated by the entrepreneur? (... ... ...)


III

The reader should notice that, where the equipment is not obsolescent but merely redundant for the time being, the difference between the actual user cost and its normal value (i.e. the value when there is no redundant equipment) varies with the interval of time which is expected to elapse before the redundancy is absorbed. (... ... ...)


IV

In Marshall's Principle of Economics (6th ed. p.360) a part of user cost is included in prime cost under the heading of 'extra wear-and-tear of plant'. But no guidance is given as to how this item is to be calculated or as to its importance. In his Theory of Unemployment (p.42) Professor Pigou expressly assumes that the marginal disinvestment in equipment due to the marginal output can, in general, be neglected: 'The differences in quantity of wear-and-tear suffered by equipment and in the costs of non-manual labour employed, that are associated with differences in output, are ignored, as being, in general, of secondary importance'.[5] Indeed, the notion that the disinvestment in equipment is zero at the margin of production runs through a good deal of recent economic theory. But the whole problem is brought to an obvious head as soon as it is thought necessary to explain exactly what is meant by the supply price of an individual firm.

  It is true that the cost of maintenance of idle plant may often, for the reasons give above, reduce the magnitude of marginal user cost, especially in a slump which is expected to last a long time. Nevertheless a very low user coast at the margin is not a characteristic of the short period as such, but of particular situations and types of equipment where the cost of maintaining idle plant happens to be heavy, and of those disequilibria which are characterised by very rapid obsolescence or great redundancy, especially if it is coupled with a large proportion of comparatively new plant.

  In the case of raw materials the necessity of allowing for user cost is obvious;ㅡif a ton of copper is used up to-day it cannot be used to-morrow, and the value which the copper would have for the purposes of to-morrow must clearly he reckoned as a part of the marginal cost. But the fact has been overlooked that copper is only an extreme case of what occurs whenever capital equipment used to produce. The assumption that there is a sharp division between raw materials where we must allow for the disinvestment due to using them and fixed capital where we can safely neglect it does not correspond to the facts;ㅡespecially in normal conditions where equipment is falling due for replacement every year and the use of equipment brings nearer the date at which replacement is necessary.

  It is advantage of the concepts of user cost and supplementary cost that they are as applicable to working and liquid capital as to fixed capital. The essential difference between raw materials and fixed capital lies not in their liability to user and supplementary costs, but in the fact that the return to liquid capital consists of a single term; whereas in the case of fixed capital, which is durable and used up gradually, the return consists of a series of user costs and profits earned in successive periods.

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