172 THE GENERAL THEORY OF EMPLOYMENT BK. IV

keep for transactions will be increased more or less pro-portionately to the increase in income; whilst, at thesame time, the cost of the convenience of plenty of readycash in terms of loss of interest will be diminished.Unless we measure liquidity-preference in terms ofwage-units rather than of money (which is convenientin some contexts), similar results follow if the increasedemployment ensuing on a fall in the rate of interestleads to an increase of wages, i.e. to an increase in themoney value of the wage-unit. In the second place,every fall in the rate of interest may, as we have justseen, increase the quantity of cash which certain indi-viduals will wish to hold because their views as to thefuture of the rate of interest differ from the marketviews.

Nevertheless, circumstances can develop in whicheven a large increase in the quantity of money mayexert a comparatively small influence on the rate ofinterest. For a large increase in the quantity ofmoney may cause so much uncertainty about thefuture that liquidity-preferences due to the security-motive may be strengthened; whilst opinion aboutthe future of the rate of interest may be so un-animous that a small change in present rates maycause a mass movement into cash. It is interestingthat the stability of the system and its sensitiveness tochanges in the quantity of money should be so dependenton the existence of a variety of opinion about what isuncertain. Best of all that we should know the future.But if not, then, if we are to control the activity of theeconomic system by changing the quantity of money,it is important that opinions should differ. Thusthis method of control is more precarious in theUnited States, where everyone tends to hold the sameopinion at the same time, than in England where differ-ences of opinion are more usual.