1. _Each grade of labor is a potential supply of desirable things and its wage is determined in essentially the same way as if it were an actual supply._ If all the various psychic goods that labor produces were spread out before men in visible form, some would be in great demand, some would exchange in a very unfavorable ratio with others. The exchange would come to equilibrium at a point where each buyer had adjusted his supply of enjoyments in the most favorable way, had so distributed his purchasing power as to get those kinds and amounts of services which afford him the highest possible sum of enjoyment. [Sidenote: Differences in wages persist] In this situation the real wages of some being so much more than those of others, the low-paid workers will have a motive to change their occupations. But the various laborers have limited abilities and cannot change at will and, despite the unfavorable ratio, they may be compelled to continue at the same work. Just as apples cannot become peaches or sheep become horses when there is a change in their price, so the unskilled workman cannot become skilled quickly, if he ever can, and the possibility of changing occupations within any reasonable period is very small indeed. Labor is constantly trying to adjust itself, to get into the better-paid industries. It moves, it emigrates, it seeks training and education. Especially the workers between the ages of fifteen and twenty-five choose the callings that promise the highest reward. Within limits an adjustment is possible, but these limits are not wide and not quickly shifted, and the wages of labor continue diverse in different occupations for an indefinite time. [Sidenote: Various grades of labor and rates of wages] 2. _The term general rate of wages can be used only of a certain grade of labor and of the rate for the average worker._ Every grade and kind of ability has its rate of wages. To be sure, it is sometimes convenient to speak in a broad but inexact way of "a general rate of wages," when comparing different countries and periods. When it is said that the rate of wages is higher in America than in England, in England than in France, in France than in India, the comparison is between men of the same occupation in the different countries; _e.g._, the unskilled laborer or the mechanic gets more here than the same grade of laborer gets in England. There is no such thing as a general rate of wages extending throughout all industries.