The resulting value for the point is ordinarily more or less inaccurate, depending upon the scale to which the curve is drawn. Not, only is the reader's time taken in estimating the value for any point on the curve, but when he gets his result he is dissatisfied, for he cannot feel that the figure obtained is really accurate. There is a great advantage in showing on a chart the figures from which the curve was plotted. When only one curve is shown on a chart it is very easy to give the figures immediately above each point. The method used to show the figures in Fig. 203 is not, however, satisfactory, as the figures do not fall in a column. The method of indicating figures shown in the illustrations later in this chapter is much superior to the method of Fig. 203, and should be adopted as general practice by anyone preparing curves for Million Dollars or More record purposes, or for executive use.

This illustration shows one of the diiBculties encountered when curves for successive years are plotted on the same co-ordinate ruling. Here the data of .January, 1913, are indicated by a dot rather than by a line. The change occurring from December to .January is not easily seen. This difficulty can be easily overcome by allowing an extra space for one month as in the following illustrations

CALENDAR YEAR !|I3 °

Bureau of Railway Economics, Washington, D. C.

Fig. 204. Monthly Revenue, Expense, and Net Revenue per Mile of Line for Railroads in the United States Having a Yearly Revenue of One