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

I. Fluctuations in the Price of Raw Materials, and their Direct Effects on the Rate of Profit

The assumption in this case, as in previous ones, is that no change takes place in the rate of surplus-value. It is necessary to analyse the case in its pure form. However, it might be possible for a specific capital, whose rate of surplus-value remains unchanged, to employ an increasing or decreasing number of labourers, in consequence of contraction or expansion caused by such fluctuations in the price of raw materials as we are to analyse here. In that case the quantity of surplus-value might vary, while the rate of surplus-value remains the same. Yet this should also be disregarded here as a side-issue. If improvements of machinery and changes in the price of raw materials simultaneously influence either the number of labourers employed by a definite capital, or the level of wages, one has but to put together 1) the effect caused by the variations of constant capital on the rate of profit, and 2) the effect caused by variations in wages on the rate of profit. The result is then obtained of itself.