(b) The _easiness_ or difficulty of learning to render acceptably a given set of personal services, will have a quick and constant influence on the Supply of these services, and of course also on the rate of the return paid for them. The elements of this Difficulty in general are time, expense, lack of natural gifts, want of foresight on the part of those concerned, and lack of push and persistency on the part of the learner himself. To put a boy apprentice to a trade, for example, requires on the part of the parents a foresight, an ability to get on without his immediate help, and sometimes also an amount of money for his board and clothes which all parents do not possess; many boys too, who must acquire their skill to sell personal services when they are young, if at all, find on trial that they do not like the trade, or have not the requisite gifts, or fail in the appropriate patience and propulsion; and the consequence is, that the Supply of laborers along that particular line is lessened, and the right to demand and the ability to secure a higher rate of wages than is accorded to common laborers accompany the small supply, through the reduction of numbers which these obstacles at the entrance occasion and the consequent weakness of competition. This is one principal ground of the difference in the wages of skilled and unskilled laborers; the other being, as we have seen, the stronger and more constant Demand for the former, owing to the impulse imparted by Capital. All these points of difficulty at the outset apply still more strongly in the case of professional laborers, serving more effectually to thin out the ranks of these, and pushing upward still higher the gauge of compensation for the successful competitors.