118 THE GENERAL THEORY OF EMPLOYMENT BK. III

extra jam has to be proportioned to the size of theadditional pill. Unless the psychological propensitiesof the public are different from what we are supposing,we have here established the law that increased em-ployment for investment must necessarily stimulate theindustries producing for consumption and thus lead toa total increase of employment which is a multiple of theprimary employment required by the investment itself.

It follows from the above that, if the marginal pro-pensity to consume is not far short of unity, smallfluctuations in investment will lead to wide fluctuationsin employment; but, at the same time, a comparativelysmall increment of investment will lead to full employ-ment. If, on the other hand, the marginal propensityto consume is not much above zero, small fluctuationsin investment will lead to correspondingly small fluctua-tions in employment; but, at the same time, it mayrequire a large increment of investment to produce fullemployment. In the former case involuntary un-employment would be an easily remedied malady,though liable to be troublesome if it is allowed todevelop. In the latter case, employment may be lessvariable but liable to settle down at a low level and toprove recalcitrant to any but the most drastic remedies.In actual fact the marginal propensity to consumeseems to lie somewhere between these two extremes,though much nearer to unity than to zero; with theresult that we have, in a sense, the worst of both worlds,fluctuations in employment being considerable and,at the same time, the increment in investment requiredto produce full employment being too great to be easilyhandled. Unfortunately the fluctuations have beensufficient to prevent the nature of the malady frombeing obvious, whilst its severity is such that it cannotbe remedied unless its nature is understood.

When full employment is reached, any attempt toincrease investment still further will set up a tend-ency in money-prices to rise without limit, irrespective