216 THE GENERAL THEORY OF EMPLOYMENT bk. iv

different hours, the consumer is expected to decide infavour of 8 o’clock, it is the business of the cook toprovide the best dinner he can for service at that hour,irrespective of whether 7.30, 8 o’clock or 8.30 is thehour which would suit him best if time counted fornothing, one way or the other, and his only task wasto produce the absolutely best dinner. In some phasesof society it may be that we could get physically betterdinners by dining later than we do; but it is equallyconceivable in other phases that we could get betterdinners by dining earlier. Our theory must, as I havesaid above, be applicable to both contingencies.

If the rate of interest were zero, there would be anoptimum interval for any given article between theaverage date of input and the date of consumption,for which labour cost would be a minimum;—a shorterprocess of production would be less efficient tech-nically, whilst a longer process would also be lessefficient by reason of storage costs and deterioration.If, however, the rate of interest exceeds zero, a newelement of cost is introduced which increases withthe length of the process, so that the optimum intervalwill be shortened, and the current input to provide forthe eventual delivery of the article will have to becurtailed until the prospective price has increasedsufficiently to cover the increased cost—a cost whichwill be increased both by the interest charges and alsoby the diminished efficiency of the shorter method ofproduction. Whilst if the rate of interest falls belowzero (assuming this to be technically possible), theopposite is the case. Given the prospective con-sumers’ demand, current input to-day has to compete,so to speak, with the alternative of starting inputat a later date; and, consequently, current input willonly be worth while when the greater cheapness, byreason of greater technical efficiency or prospectiveprice changes, of producing later on rather than now,is insufficient to offset the smaller return from negative