This incentive, conditioned by the fact of increasing returns, is always in the background. The destiny of many places is manifested in terms beyond the control of the carrier. Soil may be poor, climate or population adverse to progress. But some particular places enjoy peculiar advantages for growth. Not to stimulate new business at these points where traffic might be cultivated, even without rivals in the field, is little better than allowing it to escape over a competitor's line of rails, were they present. [Illustration: Effect of Competition at Certain Places on Rates.] Cutting the normal rate at competitive points or at important points in order to stimulate traffic, in conformity with the principle above stated, transforms our tariff diagram as shown herewith. The rate rises steadily with the increasing distance from A, except at E and F. At these points it is fixed at a lower point, determined not primarily by the cost of service at all, but by the available demand for it. Traffic at these points is charged what it will bear; not as much but as little as it will bear: which, being translated, means that the charge is set as high as possible, still holding the volume of business constant, or even increasing it if that can be accomplished. The total profit is constituted of the profit per unit of freight multiplied into its volume. The centre of interest is here shifted from the average profit per unit considered alone, to the total profit thus obtained. At this point another difficulty presents itself. Although, as set forth elsewhere, local discrimination,--charging a lower rate for a more distant point,--may sometimes not only be not injurious but actually beneficial to all parties concerned, it is the exception, not the rule.[68] Ordinarily to accord a remote point a lower rate without patent cause, is an economic anomaly, and, moreover, a political blunder. It violates the democratic principle of cost of service as underlying rate schedules. Most legislative bodies have prohibited it by law. The United States and most of the American commonwealths do not permit it, other than in exceptional cases. The result is that on our hypothetical tariff, the rates from A to points intermediate between A and B and B and D must be cut to the levels, E and F, fixed for those latter places. Such was the action taken by the trunk lines in 1887 in conformity with the requirements of the long and short haul clause of the Federal Act to Regulate Commerce. An original progressively rising tariff is thus at once transformed to a series of level grades or platforms, the shifts of level corresponding to the location of large towns or competitive centres; and the grade of each platform being fixed by the rate determined under competition at those points.[69] This ascending series of grades may be most irregular, as conditioned by local circumstances. The general steepness of the gradation is low