ore or grain, cheaply handled, or merchandise which must be carefully housed and treated; its regularity, whether it flows evenly the year round like the dressed beef business, or as on the cotton and cattle range roads, is concentrated in a short season and all moves in one direction;[36] the relative proportions of freight and passenger business--in New England about on an equality, while in the West and South nearly nine-tenths freight; and, finally, the efficiency of management, in the use of rolling stock, making up trainloads and keeping all equipment busy; all of these factors will influence the proportionate distribution of expenditures. The operation of each road thus constitutes an interesting problem in statistical analysis by itself.[37] [Illustration: _RELATION OF TRAFFIC TO MAINTENANCE OF WAY COSTS ON REPRESENTATIVE EASTERN AND WESTERN ROADS--1910_] The relation of course between density of traffic and the distribution of expenditures is direct. Heavy and frequent trains increase the wear and tear as distinct from mere depreciation from age and weather. This is demonstrated graphically by the following diagram.[38] The solid black horizontal belts to right of the centre show how low is the density of traffic on the five upper western roads by contrast with the five carriers in trunk line territory. The left hand horizontal belts show proportionally in dollars the outlay per mile of road for maintenance. Naturally the expense of such maintenance is likewise less on the western lines. But when stated, not absolutely in dollars per mile of road but in terms of utilization, as by the shaded belts to right of the centre, the true state of things appears. Density considered, in other words, the western roads are all as well kept up as those in the East. The necessity at all times of interpreting such expenditures, not in absolute figures but in terms of utilization, is obvious; and yet it is not always done in practice.