Page:Graphic methods for presenting facts (1914).djvu/174

 given on each curve since the beginning of each fiscal year. For November the average includes two months, for December three months, for January four months, etc. The progressive averages in this chart mean comparatively little and can be of almost no assistance to the manager studying them. The daily averages and the progressive averages would have been much more striking if the averages for the two years had been plotted horizontally instead of as superimposed curves. A moving average could then be shown continuously so that the average would always take in twelve months without having to start over again at the beginning of the second fiscal year. The information in Fig. 135 would have been more simple in appearance and more quickly apprehended if it had been given on two separate sheets of paper, the daily average curve and the suggested moving-average curve being shown for two years horizontally on one sheet, the cumulative curves being shown on a different sheet with the two years superimposed on the same scale, as in Fig. 135.

It is frequently desirable to show two cumulative curves on the same ruled sheet of co-ordinate paper so that each curve may be studied separately and the distances between the curves noted. Thus, in Fig. 136, the upper curve shows the amount of money loaned since the beginning of the operation of a factory loan-department. The lower curve, the dotted line, indicates the amount of money repaid by the persons obtaining loans since the beginning of the department. The difference between these two curves thus represents the amount of money outstanding at the end of any month. At the bottom of the chart the actual amount of money outstanding is plotted, also in the form of a curve. On the curve showing the amount outstanding the height of each point above the zero line represents the distance between the two cumulative curves in the upper portion of the chart. It is much easier to see fluctuations if the amount outstanding is plotted in this way from the zero line than if one must gauge the amount outstanding by reading the space between two fluctuating cumulative curves. When data must be read by the length of vertical lines between two curves, the eye is likely to take as the distance between the curves the shortest distance instead of the distance measured on the vertical ruled lines.

In Fig. 136 it was very important to watch the total amount outstanding, for the fund available for loans from the beginning of the loan system until January, 1912, was limited to $200. From January,