The plain implication of this passage is that skilled labor receives remuneration out of proportion to the quantity of labor rewarded. Therefore it is also implicit that quantity of disutility is what determines quantity of labor. Since labor cost operates upon exchange values only by way of wages cost, in so far as wages cease in fact to be an accurate index of real labor cost, a new difficulty is created for the labor theory—one very important in principle. Mill himself lays little emphasis upon this point. He regards the superior remuneration of skilled labor as due virtually to a failure of perfect competition. In presenting the subject in this light, he anticipates the important theory of non-competing groups later developed by Cairnes: “We have before remarked that the difficulty of passing from one class of employments to a class greatly superior, has hitherto caused the wages of all those classes of labourers, who are separated from one another by any very marked barrier, to depend more than might be supposed upon the increase of the population of each class, considered separately; and that the inequalities in the remuneration of labour are much greater than could exist if the competition of the labouring people generally could be brought practically to bear on each particular employment.”[167] It is hardly necessary or advisable to define perfection of competition in such broad terms as to make it require that the remuneration of skilled labor should be reduced to the standard of disutility of labor. In any event, the tendency of remuneration to approach such a level is ineffective, and therefore negligible. Static principles may be conditioned upon assumptions contrary to fact, but the assumptions are never to be made so violent that the law is not an effective force which must be apprehended before dynamic reality can be explained. Under perfect competition, properly defined, skilled labor is still a thorn in the flesh of the old theory of value. 6. It remains to summarize Mill’s view of the relation of labor cost to exchange value, and to compare it with the views of Ricardo, Malthus and Senior. In Mill’s own language we find the following summary: If one thing exchanges for more than another, the cause must be that “it requires for its production either a greater quantity of labor,” or (1) “a kind of labour permanently paid at a higher rate,” or (2) “the capital which supports that labour must be advanced for a longer period,” or, lastly, (3) “the production is attended with some circumstance which requires to be compensated by a permanently higher rate of profit.” “Of these elements, the quantity of labor required for the production is the most important; the effect of the others is smaller, though none of them is insignificant.”[168]