凯衍斯的“概论”

(3)凯衍斯的“概论”

凯衍斯(J.M.Keynes)的《雇用利息与货币的概论》(General Theory of Employment，Interestand Money)是继续他的《货币论》而作的。在那个时代，欧美各国都闹着失业(Unemployment)的严重问题。凯衍斯的理论是想从货币去设法解决这个难题。大致地说，他是主张把货币价值逐渐减低，以期达到增加利润因而增加生产因而增加劳力的需要之目的。要减低货币价值，必定要使借款利率比较地低于企业所得的利润(profit)。他认为利率减低是可以刺激生产的。全书理论很深，且所用符号与公式也与《货币论》不一样。现在只能将其梗概略为陈述之。

在叙述他的学说以前，让我们先介绍他的几个定义:

利率的定义“利率是对于在某一定时期捐除资金活动之报酬。利率从它的本身说来，不过是因为在那个时期内要把货币的支配权和一个债权相交换而产生出来的现在货币数额与将来所得之反比例。”

“...the rate of interest is the reward for parting with liquidity for a specified period.For the rate of interest is，in itself，nothing more than the inverse proportion between a sumof money and what can be obtained for parting with control over themoney in exchange for a debt for a stated period of time.”^[70]

资本的界限效率“资本的界限效率等于一种折旧率。此折旧率可使资本的资产在它的适用年龄内预期的收获用年金法计算出来的现值与其将来重购价格恰能相等。”

“I define the marginal efficiency of capital as being equal to that rate of discount which would make the present value of series of anunities given by the returns expected fromthe capital-asset during its life just equal to its supply price”，which is sometimes called the replacement cost.^[71]

消费的倾向与储蓄的倾向消费的倾向(propensity to consume)与储蓄的倾向(propensity to save)是相反的，是说消费人的心理受着客观的与主观的两种影响随时改变其消费态度。他列举客观的影响6项与主观的影响8项。所谓客观的条件(objective factors)，①工资单位的变更，②所得与净所得之差的变更，③不在净所得内计算之资本价值的意外的变更，④现在货物与未来货物相交换的比例之变更，⑤国家财政政策之变更，⑥对于现在收入平准与将来收入平准之关系发生期望上之变更。所谓主观的条件(subjective factors)，①对于不可预料的事变设立准备，即是所谓预防(precaution)，②对于日后的所得与其自己或家属的需要预为之计，譬如养老、子女教育、亲属抚养等，即是所谓远虑(Foresight)，③享受利息与资本增加，宁愿现在少用以便将来多用，即所谓计算(Calculation)，④希望生活标准逐渐提高，即是所谓改良(Improvement)，⑤希望经济独立，可以有作为，即是所谓独立(Independence)，⑥有投机或商业的计划，即是所谓企业(Enterprice)，⑦愿遗留财产，即是所谓光荣(Pride)，⑧满足受贫的志愿，对于一切用款都表反对，即是所谓悭吝(Avarice)。

凯衍斯继续他的《货币论》，讨论储蓄与投资的关系，在简括地叙述马夏律、嘉塞尔、嘉福尔(Carver)，福拉克斯(Flux)，陶昔格(Taussig)，洼尔拉斯诸家的利率学说以后，予以整个的批评。他自命为新经典学派(Neoclassical School)，与旧经典学派不同。旧派认为利率能将需要投资与愿意储蓄两方面牵引到一个平准上去，而新派则相信储蓄与投资实际上不必相等。其所以不必相等的原因，是由于收入(Income)发生变化。如其不然，则新派与旧派原无不同。这就是说，如果所得平准是一定的，现行利率必在两个曲线交叉之一点，即适应各种利率之需要资本曲线与适应各种利率之一定所得中的储蓄数量曲线相截之一点。

The Classical Theory of the Rate of Interest“regarded the rate of interest as the factor which brings the demand for investment and the willingness to save into equilibriumwith one another.Investment represents the demand for investible resources and saving represents the supply，whilst the rate of interest is the price of investible resources at which the two are equated.”^[72]

“Unlike the neo-classical school，who believe that saving and investment can be actually unequal，the classical school proper has accepted the view that they are equal.Marshall，for example，surely believed，although he did not expressly say so，that aggregate saving and aggregate investment are necessarily equal.Indeed，mostmembers of classical school carried this belief much too far;since they held that every actof increased saving by an individual necessarily brings into existence a corresponding act of increased investment...When we come to the propensity to consume and its corollary the propensity to save，we are nearer to a difference of opinion，owing tothe emphasis which they have placed on the influence of the rate of interest on the propensity to save.But they would presumably，notwish to deny that the level of income also has an important influence on the amount saved; while I，formy part，would not deny that the rate of interestmay perhaps have an influence(though perhaps notof this kind which they suppose)on the amount saved out of a given income.All these points of agreement can be summed up in a proposition which the classical school accept and I would not dispute;namely，that，if the level of income is assumed to be given，we can infer that the current rate of interest must lie at the point where the demand curve for capital corresponding to different rates of interest cuts the curve of amounts saved out of the given income corresponding to different rates of interest.”^[73]

投资超过储蓄，利润才可加多，是《货币论》的学说，前已说过。现在他还是如此主张，投资率的扩充不能超过一个界限。此界限即是资本的界限效率不再高于当时的利率。换一句话说，投资所能扩充到的一点，即是投资需要曲线的一点;在这点上，一般资本的界限效率恰等于市场利率。

“Now it is obvious that the actual rate of current investment will be pushed to the point where there is no longer any class of capital-asset of which the marginal efficiency exceeds the current rate of interest.In other words，the rate of investment will be pushed to the point on the investment demand-schedule where the marginal efficiency of capital in general is equal to the market rate of interest.”^[74]

物价上涨的希望本足以刺激生产，但如利率与资本的界限效率同样加高，则不能发生何种刺激作用。要刺激生产，必要使资本的界限效率比较地高过于利率才行。

“If the rate of interest were to rise pari passu with the marginal effi-ciency of capital，there would be no stimulating effect fromthe expectation of rising prices.For the stimulus to output depends on themarginal efficiency of a given stock of capital rising relatively to the rate of interest.”^[75]