"The conception that there is some simple correlation between the volume of aggregate demand for final goods and the total volume of employment derives from the experience of the shopkeeper that a strong demand for his goods secures his prosperity. The conception of such a relation as exists between the strength with which one may suck at one end of a pipe and the pull of the suction at the other end is of course the crudest possible misrepresentation that has been periodically reintroduced into scientific discussion, most recently and with devastating effect by Lord Keynes. The incredible crudity of this approach, congenial to the minds for whom scientific method exhausts itself in measuring the connection between changes of two observable magnitudes, ought to have been exposed long ago. The volume of employment is not determined by the relation of total demand to the total supply of goods and services but by the correspondence or non-correspondence between the distribution of demand among the different goods and services and the proportions in which these different things are offered. This applies not only to the horizontal or cross-sectional but equally to the longitudinal or vertical distribution within the stream of goods and services providing for future needs: the degree to which the volume of this stream is filled up or reduced and the corresponding shifts of demand from later to earlier stages of production or vice versa. Both these correspondence can be brought about only by appropriate changes in relative prices of the different means of production and a prompt adaptation of the quantities supplied to quantities demanded. Demand for labor is not a homogenous aggregate but an extremely diversified force with complex interactions among the parts, which defy any helpful summarization by statistics. All that is certain is that any rigidity of wages and any refusal to adjust them promptly to changing conditions must make it impossible for particular workers to find employment at the given wages, which is a condition that by various interconnections is bound to spread. Freezing the relations among the wages of different kinds of labor must produce unemployment."