The differential rate system of piece-work consists briefly, in offering two different rates for the same job, a high price per piece in case the work is finished in the shortest possible time and in perfect condition, and a low price if it takes a longer time to do the job, of if there are any imperfections in the work. (The high rate should be such that the workman can earn more per day than is usually paid in similar establishments.) This is directly the opposite of the ordinary plan of piece-work in which the wages of the workmen are reduced when they increase their productivity.