Every individual is continually exerting himself to find the most advantageous employment for whatever capital he can command. It is his own advantage, indeed, and not that of the society, Which he has in view..... [But] by directing that industry in such a manner as its produce may be of the greatest value, he [is] ... led by an invisible hand to promote an end that was no part of his intention.... By pursuing his own interest he frequently promotes that of society more effectually than when he really intends to promote it.