The magnitude and importance of the growth of tonnage, as above described, is revealed by the rapid increase in railroad earnings. The course of these is shown by the succeeding chart on page 82. Gross revenues of American railroads in 1889 were about one billion dollars. In 1910 they amounted to $2,750,000,000. Thus it appears that gross earnings almost equalled three times the amount of twenty years ago. The net income available for dividends has grown even faster. The increase was, roughly speaking, about five fold; namely, from 101 millions in 1889 to 515 millions in 1910. Nearly three and one-half times as much money went annually to the owners of railroad securities as dividends and interest, besides leaving surplus earnings for 1910 of about 222 millions available for improvements and surplus. But the limit of utilization seems to have been about reached on many roads in 1906; and an era of extensive new capital outlay to increase the existing plants and facilities ensued. Indications are not lacking to show that at the height of activity before the industrial collapse of 1907-1908, such a point of saturation had been reached, especially in trunk line territory and on the northern transcontinental lines.[55] On the Northern Pacific, for instance, the ton mileage increased from 2.2 billions to 5.2 billions between 1900 and 1906. The Northwest was suddenly confronted at that time with the new issue of enlarging facilities, which had been slowly becoming apparent elsewhere in the country during the preceding decade. Grain actually rotted on the ground, and an acute coal famine occurred, because of sheer inability of the roads to care for the new traffic. Changes in methods of business also somewhat exaggerated this strain upon the carriers. Merchants now expect quick delivery to order. They object to stocking up months ahead, even when conditions are auspicious; therefore, business, when especially stimulated, comes with an irresistible rush. All these causes, coupled with undiscriminating attempts by inadequately bedded roads to imitate the methods of progressive ones by prematurely increasing their train loads, led to a practical breakdown of the transportation business of the country in the autumn of 1906. To the student of transportation, this congestion denoted the attainment of a point of saturation for the then-existing physical plant. The analogy to the case of the Pennsylvania Railroad, previously described, is obvious. Such a predicament is bound to arise in the development of any carrier in a rapidly growing country. Its fiscal significance will appear in due time. A comparison of the growth of business and of operating expenses for the entire railroad system of the United States over a series of years is given in the following table. The results are expressed by means of index numbers based upon the year 1880, taken as 100.[56]