The commercial worker produces no surplus-value directly. But the price of
 his labour is determined by the value of his labour-power, hence by its costs
 of production, while the application of this labour-power, its exertion,
 expenditure of energy, and wear and tear, is as in the ease of every other
 wage-labourer by no means limited by its value. His wage, therefore, is not
 necessarily proportionate to the mass of profit which he helps the capitalist
 to realise. What he costs the capitalist and what he brings in for him, are two
 different things. He creates no direct surplus-value, but adds to the
 capitalist's income by helping him to reduce the cost of realising
 surplus-value, inasmuch as he performs partly unpaid labour. The commercial
 worker, in the strict sense of the term, belongs to the better-paid class of
 wage-workers — to those whose labour is classed as skilled and stands
 above average labour. Yet the wage tends to fall, even in relation to average
 labour, with the advance of the capitalist mode of production. This is due
 partly to the division of labour in the office, implying a one-sided
 development of the labour capacity, the cost of which does not fall entirely on
 the capitalist, since the labourer's skill develops by itself through the
 exercise of his function, and all the more rapidly as division of labour makes
 it more one-sided. Secondly, because the necessary training, knowledge of
 commercial practices, languages, etc., is more and more rapidly, easily,
 universally and cheaply reproduced with the progress of science and public
 education the more the capitalist mode of production directs teaching methods,
 etc., towards practical purposes. The universality of public education enables
 capitalists to recruit such labourers from classes that formerly had no access
 to such trades and were accustomed to a lower standard of living. Moreover,
 this increases supply, and hence competition. With few exceptions, the
 labour-power of these people is therefore devaluated with the progress of
 capitalist production. Their wage falls, while their labour capacity increases.
 The capitalist increases the number of these labourers whenever he has more
 value and profits to realise. The increase of this labour is always a result,
 never a cause of more surplus-value.[2]