CH. 4 THE CHOICE OF UNITS 41

measure of current aggregate output, such as wouldenable us to compare its amount with the amountwhich would result from the association of a differentcapital equipment with a different quantity of employ-ment. When, for purposes of description or roughcomparison, we wish to speak of an increase of output,we must rely on the general presumption that theamount of employment associated with a given capitalequipment will be a satisfactory index of the amount ofresultant output;—the two being presumed to increaseand decrease together, though not in a definite numeri-cal proportion.

In dealing with the theory of employment I propose,therefore, to make use of only two fundamental unitsof quantity, namely, quantities of money-value andquantities of employment.‘The first of these is strictlyhomogeneous, and the second can be made so. For,in so far as different grades and kinds of labour andsalaried assistance enjoy a more or less fixed relativeremuneration, the quantity of employment can besufficiently defined for our purpose by taking anhour’s employment of ordinary labour as our unit andweighting an hour’s employment of special labour inproportion to its remuneration;.e. an hour of speciallabour remunerated at double ordinary rates will countas two units. We shall call the unit in which thequantity of employment is measured the labour-unit;and the money-wage of a labour-unit we shall call thewage-unit.1 Thus, if E is the wages(and salaries) bill,W the wage-unit, and N the quantity of employment, E = N. W.

This assumption of homogeneity in the supply oflabour is not upset by the obvious fact of great differ-ences in the specialised skill of individual workersand in their suitability for different occupations. For,

1 If X stands for any quantity measured in terms of money, it willoften be convenient to write Xω for the same quantity measured in terms ofthe wage-unit.