62 THE GENERAL THEORY OF EMPLOYMENT BK. II

The criterion must obviously correspond to where wedraw the line between the consumer and the entre-preneur. Thus when we have defined A1 as the valueof what one entrepreneur has purchased from another,we have implicitly settled the question. It followsthat expenditure on consumption can be unambigu-ously defined as Σ(A - A1), where is the total salesmade during the period and ΣA1 is the total sales madeby one entrepreneur to another. In what follows itwill be convenient, as a rule, to omit Σ and write A forthe aggregate sales of all kinds, A1 for the aggregatesales from one entrepreneur to another and U for theaggregate user costs of the entrepreneurs.

Having now defined both income and consumption ,the definition of saving , which is the excess of incomeover consumption, naturally follows. Since income isequal to A - U and consumption is equal to A - A1,it follows that saving is equal to A1 - U. Similarly,we have net saving for the excess of net income overconsumption, equal to A1 - U - V.

Our definition of income also leads at once to thedefinition of current investment. For we must meanby this the current addition to the value of the capitalequipment which has resulted from the productiveactivity of the period. This is, clearly, equal to whatwe have just defined as saving. For it is that partof the income of the period which has not passedinto consumption. We have seen above that as theresult of the production of any period entrepreneursend up with having sold finished output having a valueA and with a capital equipment which has suffered adeterioration measured by U (or an improvementmeasured by - U where U is negative) as a result ofhaving produced and parted with A, after allowing forpurchases A1 from other entrepreneurs. During thesame period finished output having a value A - A1 willhave passed into consumption. The excess of A - Uover A - A1, namely A1 - U, is the addition to capital