124 THE GENERAL THEORY OF EMPLOYMENT BK. III

and partly by the higher prices causing a depletionof stocks. So far as the balance is restored by a post-ponement of consumption there is a temporary re-duction of the marginal propensity to consume, i.e.of the multiplier itself, and in so far as there is a de-pletion of stocks, aggregate investment increases forthe time being by less than the increment of investmentin the capital-goods industries,— i.e. the thing to bemultiplied does not increase by the full increment ofinvestment in the capital-goods industries. As timegoes on, however, the consumption-goods industriesadjust themselves to the new demand, so that when thedeferred consumption is enjoyed, the marginal pro-pensity to consume rises temporarily above its normallevel, to compensate for the extent to which it previ-ously fell below it, and eventually returns to its normallevel; whilst the restoration of stocks to their previousfigure causes the increment of aggregate investmentto be temporarily greater than the increment of invest-ment in the capital-goods industries (the increment ofworking capital corresponding to the greater outputalso having temporarily the same effect).

The fact that an unforeseen change only exercisesits full effect on employment over a period of time isimportant in certain contexts;—in particular it playsa part in the analysis of the trade cycle (on lines suchas I followed in my Treatise on Money). But it does notin any way affect the significance of the theory of themultiplier as set forth in this chapter; nor render itinapplicable as an indicator of the total benefit to em-ployment to be expected from an expansion in thecapital-goods industries. Moreover, except in con-ditions where the consumption industries are alreadyworking almost at capacity so that an expansion of out-put requires an expansion of plant and not merely themore intensive employment of the existing plant, thereis no reason to suppose that more than a brief intervalof time need elapse before employment in the con-