Operating expenses ($67 plus forty per cent. of ten per cent. of $67) $ 69.68 Fixed charges as before $ 28.00 ------- $ 97.68 Income, increased by ten per cent. $110.00 ------- Balance for profit or dividends $ 12.32 By an increase of ten per cent. in tonnage, balance for dividends has more than doubled. In this connection it will be noted that a constant rate of return per unit of business newly acquired has been assumed. Attempts were made on behalf of the railroads, during the long period of decline of ton mile revenue down to 1900, by Newcomb and others, to show that this is an unreasonable assumption; in that increased traffic is presumably to be had only by a progressive lowering of the rates charged. This contention has been effectively demolished by the steady and remarkable growth of traffic since 1900, even in the face of a substantial rise of rates all along the line. A necessary corollary to our proposition, beside that of the maintenance of a constant scale of charges, is, of course, also of the continuance of a given grade of service and of costs of operation. If more luxuriously appointed passenger trains or quicker freight service have to be given in order to produce the growth of business, the added costs of operation must, naturally, be taken into consideration. If widespread rise of wages follows an increase in the general cost of living, that too is an entirely extraneous factor. But with a given grade of service, constant rates and steady wage scales, there can be no question, up to the point of full utilization of the existing plant, that the operation of railroads affords clear demonstration of the law of increasing returns. The obverse side of the law of increasing returns is also of great importance. For the same reason that when traffic increases, only a portion of the expenses are affected, it follows that, when business declines, only a part of the costs can be lopped off. In other words, a reduction in the volume of traffic does not in itself alone lead to a corresponding reduction in the operating expenses. Of course, many of these latter may, as we have seen, be temporarily postponed, as they were in 1893-1897, especially in the group of maintenance-of-way expenses. In such an event they must ultimately be made good by extraordinary outlay at some later time. But, unless they be thus postponed and unless the rates charged for service be reduced in order to stimulate traffic, it is inevitable that the margin of profit will drop as rapidly as it tends to rise with increased volume of business. This may be illustrated by the following computation.[52] Assume the total revenue from a given business to be $100, and assume it to be distributed as before, viz.: