Capital, Volume Three: The Process of Capitalist Production as a Whole by Karl Marx

I. In General

The increase of absolute surplus-value, or the prolongation of surplus-labour, and thus of the working-day, while the variable capital remains the same and thus employs the same number of labourers at the same nominal wages, regardless of whether overtime is paid or not, reduces the relative value of the constant capital as compared to the total and the variable capital, and thereby increases the rate of profit, again irrespective of the growth of the quantity of surplus-value and a possibly rising rate of surplus-value. The volume of the fixed portion of constant capital, such as factory buildings, machinery, etc., remains the same, no matter whether these serve the labour- process 16 or 12 hours. A prolongation of the working-day does not entail any fresh expenditures in this, the most expensive portion of constant capital. Furthermore, the value of the fixed capital is thereby reproduced in a smaller number of turnover periods, so that the time for which it must be advanced to make a certain profit is abbreviated. A prolongation of the working-day therefore increases the profit, even if overtime is paid, or even if, up to a certain point, it is better paid than the normal hours of labour. The ever-mounting need to increase fixed capital in modern industry was therefore one of the main reasons prompting profit-mad capitalists to lengthen the working- day. 1 The same conditions do not obtain if the working-day is constant. Then it is necessary either to increase the number of labourers, and with them to a certain extent the amount of fixed capital, the buildings, machinery, etc., in order to exploit a greater quantity of labour (for we leave aside deductions from wages or the depression of wages below their normal level), or, if the intensity and, consequently, the productivity of labour, increase and, generally, more relative surplus-value is produced, the magnitude of the circulating portion of constant capital increases in such industrial branches which use raw materials, since more raw material, etc., is processed in a given time; and, secondly, the amount of machinery set in motion by the same number of labourers, therefore also this part of constant capital, increases as well. Hence, an increase in surplus-value is accompanied by an increase in constant capital, and the growing exploitation of labour by greater outlays of the means of production through which labour is exploited, i.e., by a greater investment of capital. Therefore, the rate of profit is thereby reduced on the one hand while it increases on the other.