It is important to take note of the historical character of this phenomenon. While the purchase and sale of labor power has existed from antiquity,* a substantial class of wage-workers did not begin to form in Europe until the fourteenth century, and did not become numerically significant until the rise of industrial capitalism (that is, the production of commodities on a capitalist basis, as against mercantile capitalism, which merely exchanged the surplus products of prior forms of production) in the eighteenth century. It has been the numerically dominant form for little more than a century, and this in only a few countries. In the United States, perhaps four-fifths of the population was self-employed in the early part of the nineteenth century. By 1870 this had declined to about one-third and by 1940 to no more than one-fifth; by 1970 only about one-tenth of the population was self-employed. We are thus dealing with a social relation of extremely recent date. The rapidity with which it has won supremacy in a number of countries emphasizes the extraordinary power of the tendency of capitalist economies to convert all other forms of labor into hired labor.