Reductions in prices made only to increase sales, 626.—Absolute and relative responsiveness of sales, 627.—Factors determining the absolute responsiveness of sales, 628.—Absolute and relative responsiveness as differentiating competitive and monopolistic price-making, 630.—The law of increasing returns and price-making, 631.—Consumers' leagues and limitation of monopoly prices, 632.—Responsiveness of business, the law of increasing returns, and discrimination, 633.—Detailed statement of the elements to be considered in price-making and mathematical expression of these elements, 634.